Hey everyone!
Yesterday, I posted about a guide I'd made on youtube on elemental reactions, approaching subjects as easy as what the elements are, then working my way to more complex subjects like elemental gauge and internal cooldown. The reception was very mixed, with half the comments telling me not to self advertise.
Considering the fact I put over 15 hours of work into that (non-monetized by the way) video just on writing the script, recording and editing, without including the research I'd made prior, I was somewhat distraught that this was the only thing people took away from my attempt at making an educational guide. Since I'd written a script for the video, I figured I might as well just work on the format of the script and transform it into a written guide, because there's no way I'm letting all that effort go to waste when I just wanted to make a resource people could refer to. With that said, enjoy the guide!
(If you want to watch the video, I'll include a link at the end)

TABLE OF CONTENTS

• New Player level

1. Elements
2. Elemental Resonance
3. Elemental Reactions
4. Aura VS Trigger

• Casual Player level

1. Multiplicative Reactions : Melt and Vaporize
2. Transformative Reactions
3. Overloaded
4. Electro-Charged
5. Frozen/Shatter
6. Superconduct
7. Swirl
8. Crystallize

• Theorycrafter level

1. Internal Cooldown (ICD)
2. Elemental Gauge
3. Gauge in Overloaded and Superconduct
4. Gauge in Multiplicative Reactions
5. Gauge with Diluc
6. Gauge with Ganyu
7. Gauge with Tartaglia (Childe)
8. "Gauge" with Bennett
9. Gauge with Klee
10. Gauge with Xiangling
11. Other reactions
12. Gauge in Swirl and Crystallize
13. Gauge with Ningguang, Sucrose and... Xiao??
14. Decay Rate + Aura Extension

• Conclusion

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NEW PLAYER LEVEL

Elements

There are currently 7 elements in the game. Players can currently play as characters of the following elements :

• Hydro : Barbara, Mona, Tartaglia (Childe), Xingqiu
• Pyro : Amber, Bennett, Diluc, Klee, Xiangling, Xinyan
• Electro : Beidou, Fischl, Keqing, Lisa, Razor
• Cryo : Ganyu, Chongyun, Diona, Kaeya, Qiqi
• Anemo : Jean, Sucrose, Traveler (Anemo), Venti, Xiao
• Geo : Ningguang, Noelle, Traveler (Geo), Zhongli, Albedo

However, we currently don’t have any dendro units. When using certain talents from those characters, you can apply their respective element to enemies or trigger elemental reactions.
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Elemental Resonance

While building your team, you can benefit from a bonus called "Elemental Resonance" if you use certain elements. Using units of certain elements will give you the following buffs :

• 2 Anemo units (Impetuous Winds) : Decrease Stamina Consumption by 15%, increase Movement SPD by 10% and shorten Skill Cooldown by 5%. This resonance isn't particularly strong in combat, but it can be very nice to use while exploring, meaning using two anemo units in an overworld team is recommended when doing exploration-related things, like hunting chests, anemoculi or geoculi.
• 2 Hydro units (Soothing Water) : Increase incoming healing by 30%. Your characters will also be affected by Pyro for 40% less time. This means that, when you're hit with a pyro ability, you'll be affected by the Pyro aura for 40% less time. We'll get into what auras are a bit later. This resonance isn't particularly useful, since most healing-dedicated units (Barbara, Bennett, Diona, Jean, Qiqi) already heal enough without that 30% bonus to keep you alive. There are still units that can benefit from it, namely Xingqiu and Noelle, but I don't recommend building teams without one of the healers mentioned earlier so the uses for this resonance are very limited.
• 2 Pyro units (Fervent Flames) : Increase ATK by 25%. You will also be affected by Cryo for 40% less time. This resonance looks very strong, but it should not be overestimated. While 25% ATK is definitely useful, keep in mind this kind of ATK buff only applies to base ATK, i.e. the white number on the left when you click on your attributes and look at your attack. Base ATK is calculated from your character's base ATK and your weapon's base ATK, meaning artifacts won't change it. This means that if you have 800 base ATK and 1000 bonus ATK from your artifacts, the 25% ATK bonus will only give you 200 more ATK, going from 1800 to 2000. It is still definitely useful, and definitely the most versatile buff, but not as strong as it initially appears.
• 2 Cryo units (Shattering Ice) : Increase your CRIT Rate against enemies that are Frozen or affected by Cryo by 15%. You will also be affected by Electro for 40% less time. This buff is VERY strong in teams where the condition is easily met, but it unfortunately doesn't work in many teams. It is mostly useful in Perma-Freeze comps, that don't trigger reactions to take the Cryo aura away from enemies, or in comps that deal most of their damage through melting Cryo-affected enemies, like the Bennett DPS comp, which we will be explaining later.
• 2 Geo units (Enduring Rock) : Increase your resistance to interruption. Increase your DMG by 15% when you're protected by a shield. This buff affects DMG, not ATK, making it generally stronger than the Pyro buff, however it should be noted that its condition isn't easily met in every team. Also, this will only increase the damage of your on-field character, unlike the Pyro resonance, which will increase the damage of ALL your characters, so it's mostly good for hypercarries that deal most of their team's damage.
• 4 units of different elements (Protective Canopy) : Increase your Elemental and Physical RES by 15%. Since this is a defensive buff, it isn't particularly useful in a game where the difficulty comes in the form of short timers instead of strong enemies, so you shouldn't be aiming for this buff.

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Elemental Reactions

Don't make the mistake of prioritizing Elemental Resonance over everything else. While it can be good, it shouldn't be your main focus when building your team. Your main focus should generally be on elemental reactions, that happen when using two DIFFERENT elements on enemies :

• Electro-Charged : Hydro + Electro. Damage over time effect which can spread to nearby enemies in certain scenarios.
• Frozen : Hydro + Cryo. Stops enemies from moving. Attacking those enemies with a heavy attack (Geo attack, Claymore attack or Plunge attack) will cause Shatter, dealing physical damage.
• Vaporize : Hydro + Pyro. Amplifies the damage of the attack that triggers it.
• Melt : Cryo + Pyro. Amplifies the damage of the attack that triggers it.
• Superconduct : Deals a small amount of damage and reduces your foes' physical RES.
• Overloaded : Deals a bigger amount of damage and knocks foes away.
• Swirl : Hydro/Pyro/Cryo/Electro + Anemo. Spreads the initial element to nearby enemies, dealing some damage. Once you unlock the Viridescent Venerer artifact set, this will also reduce those enemies' elemental RES.
• Crystallize : Hydro/Pyro/Cryo/Electro + Geo. Does not deal ANY damage, but generates a shard on the ground, which you can pick up to gain a shield.

You may notice there is no reaction for Geo + Anemo. In order to understand why that is, we have to understand the difference between an aura and a trigger.

Aura VS Trigger

An elemental reaction occurs when two elements meet each other. For this to happen, one element must be present on an enemy when attacking them with another element. The trigger element, as its name suggests, is the element that triggers the reaction, or the 2nd element applied. The aura element, on the other hand, is the element that is initially applied to an enemy, and which stays there as an aura. Aura elements don't do anything by themselves, with the exception of the Cryo Aura, which slows enemies down. The reason there is no Geo + Anemo reaction is simply that neither Geo nor Anemo can be an aura element. When using a Geo or an Anemo ability on an enemy, it will NOT leave a Geo or Anemo aura on them.
Aura VS trigger also matters in determining the damage dealt by elemental reactions. The damage of a reaction will ALWAYS scale with the trigger character’s stats, and NOT the aura character. You can easily demonstrate this by using a low level character and a high level character. When your trigger character is the high-level one, the damage is much higher than when your trigger character is the low-level one.
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​

CASUAL PLAYER LEVEL

Multiplicative Reactions : Melt and Vaporize

Multiplicative reactions, also called amplifying reactions, are the most simple. They simply multiply the damage of the attack that triggers them. There are currently only 2 multiplicative reactions : Melt and Vaporize. Both of these reactions have different multipliers depending on the element that triggers them.
Triggering Melt with a Pyro ability will multiply its damage by 2 (Strong-Side), while triggering it with a Cryo ability will multiply its damage by 1.5 (Weak-Side).
Similarly, triggering Vaporize with Hydro multiplies its damage by 2 (Strong-Side), while triggering it with Pyro multiplies is damage by 1.5 (Weak-Side).
Multiplicative reactions are generally considered stronger late-game options, as since they multiply the damage of the attack that triggers them, they don’t ONLY scale with Elemental Mastery, but also scale with ATK, CRIT stats and DMG% stats.
Multiplicative reactions’ biggest weakness is how hard it can be to set them up properly, because of some interactions we’ll be talking about later.
Their biggest strength is the overall damage multiplier they bring to a team, as is the case in the following comps :
Bennett+Chongyun : Melt-focused comp, the only real late game Strong-Side team comp
Diluc+Xingqiu : Vaporize-focused comp, the most versatile Weak-Side team comp
Ganyu+Xiangling : Melt-focused comp, the highest DPS ceiling, and a Weak-Side comp
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Transformative Reactions

Transformative reactions, on the other hand, deal damage based on your character’s LEVEL and ELEMENTAL MASTERY ONLY. This means their damage will not change depending on the attack you use to trigger them, simply on the character you use. For example, if you were to trigger superconduct with Kaeya and Lisa, you would get different numbers when using Kaeya as the trigger as you would using Lisa as the trigger, but you would get the SAME number using Lisa’s Normal Attack as the trigger as you would with Lisa’s skill.
Because Transformative reactions only scale with Level and Elemental Mastery, and since their base damage doesn't scale particularly well with level, they are generally considered weaker damage alternatives in the late game.
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Overloaded

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Level	1	10	20	30	40	50	60	70	80	90
Base DMG	34	60	143	243	375	579	886	1287	1697	1924

The highest damage out of all the transformative reactions, it's also generally considered to be one of, if not the, weakest. In order to deal with enemies quickly, you generally want to keep enemies grouped together, letting you hit multiple enemies at once with your AOE (Area of Effect) attacks. However, Overloaded pushes enemies away from you, and most importantly, from each other. This makes it hard to deal with multiple enemies at once, and will often make you lose DPS (Damage per second), rather than making you gain DPS.
Overloaded still has some late-game uses : It can destroy geo shields and keep enemies away from the monolith. However, it isn't the fastest way to destroy geo shields, making it hard to justify. This means its only realistic late-game use is in the rare protect the monolith stage.
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Electro-Charged

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Level	1	10	20	30	40	50	60	70	80	90
Base DMG	20	38	86	145	225	349	533	771	1019	1171

Electro-Charged actually works in a different way than other reactions, as you can have both a Hydro AND an Electro aura active on a character at the same time. This means you can use ONE ability to trigger TWO reactions on an electro-charged enemy. For example, you can use a pyro ability on an electro-charged target to trigger vaporize AND overloaded. The specifics on the inner workings of the Electro-Charged mechanic are slightly more complicated, so I'll be making a post in the future on the details. Electro-Charged isn’t an insanely strong reaction, but unlike Overloaded, it doesn’t have any actual downside, so you have no reason to actively avoid it.
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Frozen/Shatter

Frozen immobilizes your opponent for a short duration, and will not deal any damage. However, any heavy attack on a frozen target will cause shatter, dealing physical damage based on the stats of the character who triggers SHATTER, not the character who triggers Frozen.
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Level	1	10	20	30	40	50	60	70	80	90
Base DMG	28	45	107	183	283	435	664	964	1275	1458

While an enemy is frozen, they are considered to be affected by a cryo aura for reaction purposes. This means you can trigger Melt with a Pyro ability, or Superconduct with an electro ability. However, the biggest strength of the Frozen reaction lies in keeping enemies frozen, without triggering another reaction or shatter. This will have two main benefits.

1. Keeping certain enemies frozen prevents them from generating or using their shields, such as Fatui Skirmishers, who won't be able to generate their shields, and Mitachurls (Wooden Shield, Rock Shieldwall and Ice Shieldwall), against whom your attacks will ignore shields while they are frozen. It’ll also keep certain other enemies, such as the Eye of the Storm or Cicin mages, from running away from you.
2. Keeping enemies frozen gives you access to the strongest situational artifact set in the game, Blizzard Strayer. The 4-piece set gives you 40% CRIT Rate against frozen enemies, which is an INSANE amount of stats if you manage to keep enemies in that state. Unfortunately, the Blizzard Strayer set is relatively weak on Claymore Cryo units, such as Chongyun, since his attacks will Shatter, making you lose out on the effect. The damage you get from Shatter is unfortunately not high enough to justify running Shatter comps over Perma-Freeze comps.

Superconduct

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Level	1	10	20	30	40	50	60	70	80	90
Base DMG	7	16	36	60	94	145	222	321	424	487

Superconduct, unlike the other reactions we’ve seen so far, deals completely insignificant damage. However, it makes up for that lack of damage with a very useful effect : It reduces the enemies’ physical RES by 40%. Note that RES reduction is only half as effective once the enemies’ RES is below 0, so using superconduct on an enemy with 10% RES would bring them to -15%, not to -30%, since the first 10% will be fully applied, then the remaining 30% will be halved.
Superconduct is used mainly for Physical carries such as Razor, Xiangling with Crescent Pike, or sometimes Keqing. Since the debuff lasts for a decently long amount of time, you don’t need to trigger it very often, letting you get away with high cooldown supports. Technically, Superconduct can have some sort of resonance effect, where it deals more damage if enemies are clustered together, but this isn’t practical, as the damage increase is only significant when multiple enemies are clustered together, and that’s generally quite hard to do with a very low payoff.
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Swirl

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Level	1	10	20	30	40	50	60	70	80	90
Base DMG	12	18	43	73	112	173	266	387	511	578

Swirl’s damage, much like Superconduct, is quite low. It can be used to spread elements, but once you reach Adventure Rank 25, you unlock the domain that can reward you with the Viridescent Venerer artifact set, which makes swirl a vital element to multiple late game teams. The 4-piece set bonus decreases opponent’s Elemental RES to the element infused in the swirl triggered by a unit that holds this set by 40%. This RES reduction works just like the RES reduction from Superconduct. That, paired with the fact the base damage is quite low, makes Swirl the elemental equivalent to Superconduct.
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Crystallize

Crystallize is the only elemental reaction that does not deal ANY damage. It drops a shard of the element you crystallized, and the shield it generates is much more effective against that element.

Level	1	10	20	30	40	50	60	70	80	90
Base Shield	91	159	304	438	557	715	896	1096	1277	1424

Unfortunately, crystallize shields are much weaker than shields generated by some units’ talents. On top of that, since geo characters don’t deal more damage based on their elemental mastery, making your crystallize shields stronger costs you the opportunity of dealing more damage, which is generally not a worthwhile tradeoff. Crystallize’s main usage is generating shields for units wearing the 4-piece Retracing Bolide set, or making use of effects that do something when elemental reactions are triggered, such as Fischl’s ascension 4 passive. It can also be used in conjunction with the 4-piece Archaic Petra set to buff your party’s elemental damage, although you have to make sure you pick up the crystal with the unit wearing the 4-piece Archaic Petra set in order to get the damage bonus.
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THEORYCRAFTER

Internal Cooldown

Internal Cooldown (ICD), the most simple of the two concepts, is about the principle that certain talents don’t always apply their own element. This can make it harder to trigger elemental reactions in quick succession. ICD is unique to every talent, which means you can trigger two reactions almost immediately if they do not share an ICD, but you can NOT cause reactions in quick succession if the trigger talent has an ICD.
I’ve found that the best way to visualize ICD is to test it against either the Anemo Hypostasis, as no matter how many reactions you trigger, it will not lose their innate element. You can then look for the time between every Swirl reaction, and that will give you a rough estimation of the ICD.
Kaeya's Burst and Fischl's Skill have long ICDs and don't swirl on every hit : https://streamable.com/5jzzu0
Xiangling's Burst has either a short ICD or no ICD at all, since it swirls on every hit. Xingqiu's Burst has a separate ICD for every time it throws swords, as it swirls every time a group of swords hits : https://streamable.com/8q8n2o
However, note that this is not always an accurate representation, as triggering multiple reactions in a row will not always show the reaction text even if the reactions do happen, as is the case when you use Chongyun’s burst.
Chongyun's Burst has no ICD, so it deals damage, but the reactions happen so fast the swirl text doesn't show up : https://streamable.com/u6fkwj
As you can see, different units often have different internal cooldowns on their talents, making it very hard to correctly assess the strength of a unit without testing.
Not understanding ICD might make you think certain combinations are much stronger than they actually are. A good example of this would be Kaeya+Xiangling. While Kaeya’s icicles hit enemies much faster than Xiangling’s pyronado, it also applies cryo at a much slower rate. This means that, when using Xiangling’s burst after using Kaeya’s, the first few hits from Xiangling’s burst will Melt, but since the pyro element is being applied faster than the cryo element, it will soon be Kaeya’s burst that starts triggering the Melts. Unfortunately, since the cryo application does have a relatively long ICD, only SOME of the icicles will Melt, leading to an overall poor use of elemental reactions that only ends up being a small damage boost.
Before we can talk about the ways we can use our knowledge of ICD to get damage boosts bigger than the ones we get from the Xiangling+Kaeya combo, we have to talk about the second concept in this section.
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Elemental Gauge

Elemental Gauge is something that seems a bit scary to approach at first, but practically, it can be simplified as basically just glorified addition and subtraction.
Every talent that applies an element to enemies applies a certain amount of Gauge Units. This can be either 1, 2, or 4. As far as I’m aware, the only way to apply 4 Gauge Units is currently Beidou’s elemental Burst’s initial hit.
The higher the amount of Gauge Units, the longer the aura stays on an enemy :

• A 1 Gauge Unit, which we’ll be calling 1U, or 1 unit, skill, will apply an aura for 9.5 seconds.
• A 2U skill will apply an aura for 12 seconds.
• A 4U skill will apply an aura for 16.8s seconds.

Timing the duration of an aura is the best way to figure out the Gauge strength of a talent, but if, like me, you’re too lazy for that, here's a table on every character and their respective talents’ gauge strength (Credits to IonFox).

Unit	Normal Attack	Charged Attack	Elemental Skill	Elemental Burst
Diluc	Infused : 1U		1U	1U
Klee	1U	1U	Bomb : 2U Mines : 1U	1U
Amber		2U	2U	1U
Bennett			Press : 2U Hold : 1U	2U
Xiangling			1U	1U
Xinyan			1U	1U
Keqing	Infused : 1U		Initial : 1U Re-cast : 2U Explosion : 2U	1U
Beidou			2U	Cast : 4U Buff : 1U
Fischl		1U	1U	2U
Lisa	1U	1U	Press : 1U Hold : 2U	1U
Razor			2U	Cast : 2U Buff : 1U
Mona	1U	1U	1U	Cast : 1U Pop : 2U
Tartaglia (Childe)	Riptide Flash : 1U Riptide Burst : 2U	1U	Cast : 2U Infusion : 1U Riptide Slash : 1U	2U (every hit)
Barbara	1U	1U	1U
Xingqiu			1U	1U
Ganyu		Arrow : 1U Bloom : 1U	1U	1U
Qiqi			1U	2U
Chongyun			Cast : 2U Infusion : 1U	1U
Diona		1U	1U	1U
Kaeya			2U	1U
Jean			2U	2U
Venti		1U	2U	1U
Traveler (Anemo)			1U	1U
Sucrose	1U	1U	1U	1U
Albedo			1U	1U
Zhongli			Cast : 2U Pulse : 1U	4U
Ningguang	1U	1U	1U	1U
Noelle	Infusion : 1U		2U	1U
Traveler (Geo)			2U	2U

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Gauge in Overloaded and Superconduct

This is where the subtraction comes in. Quite simply, the strength of the trigger is subtracted from the strength of the aura. That means that if you use a 2U aura, then a 1U trigger, the initial aura will stay on the enemy, because 2-1>0
Any other combination of 1U and 2U will remove the aura, because 1-1, 1-2 and 2-2 are all equal or under 0.
A 4U aura will not be removed by a 2U trigger, nor by 3 1U triggers, meaning you can get a lot of reactions done with a 4U aura. Unfortunately, we only have one 4U talent that can apply an aura and it’s on a burst, so practical applications of 4U auras are very limited.
There is one thing you have to keep in mind when trying to trigger multiple reactions without reapplying the aura : the elemental gauge’s strength goes down over time. This means if you wait for one of the units of a 2U aura to decay, a 1U trigger will remove the aura.
Technically, the decay rate isn’t exactly linear, but we can use an approximation here, since it’s almost linear and it generally won’t make much of a difference. Unfortunately, as I mentioned in the CASUAL section for transformative reactions, Overloaded and Superconduct generally don’t offer great late game scaling, making the practical uses of gauge knowledge in these reactions mostly irrelevant.
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Gauge in Multiplicative Reactions

Here is where the practical uses of gauge knowledge come in. Much like transformative reactions, triggering multiplicative reactions removes a certain quantity of gauge from an enemy. However, unlike transformative reactions, a 1U trigger does NOT remove 1 unit of gauge. A 1U trigger will either remove HALF a unit or TWO units. Why?
Basically, just like melt and vaporize have different DAMAGE multipliers depending on the element that triggers them, they also have different GAUGE multipliers. This means triggering the WEAK side of a melt or vaporize reaction will divide the amount of gauge units REMOVED by that reaction by 2. Triggering the STRONG side of such a reaction will MULTIPLY the amount of gauge units removed by 2.
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https://preview.redd.it/ql0faut7fpd61.png?width=855&format=png&auto=webp&s=802e52043df05995489d1790f4928802197e5113
This means using a 2U cryo aura, you can only trigger ONE melt reaction no matter what trigger you use, because a 1U pyro trigger will be multiplied by 2 and remove both of the cryo units. The same could be said about 2U Pyro auras and Hydro triggers.
HOWEVER, when using pyro auras for melt or hydro auras for vaporize, you can EASILY trigger multiple reactions.
With a 2U aura, you can trigger more than one reaction with a 2U trigger, because 2-(0.5x2)>0. You could also theoretically trigger up to FOUR reactions with 1U triggers,
A good application of this is Chongyun’s Burst’s triple melt combo. This works because both Bennett’s burst and Bennett’s skill are 2U, meaning either can easily sustain the first two 1U triggers of Chongyun’s burst, leaving a pyro aura for the third trigger to melt, leading to a triple melt. This combo only works because Chongyun's Burst, unlike Kaeya's Burst, has no ICD, meaning you can trigger the three melts in quick succession.
Chongyun Triple Melt makes Pyro Plant go bye-bye (not exactly a 1 shot but my chongus is level 50 so i'll take it) : https://streamable.com/j0fnzo
If the aura is 1U, you won’t be able to trigger two reactions with 2U triggers, but you WILL be able to trigger two reactions with 1U triggers. Both of the units with the highest DPS ceilings in the game, Ganyu and Diluc, can actually use this mechanic to significantly increase their damage.
Every. Single. One. Of their talents apply a 1U gauge. This means that as long as you have a way to consistently apply 1U auras, you’ll be able to vaporize, in Diluc’s case, or melt, in Ganyu’s most of their damage. Let’s now take a look at a few comps that use elemental gauge mechanics quite well.
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Gauge with Diluc

With Diluc, this is done by using Xingqiu. Xingqiu’s elemental burst will re-apply a 1U hydro gauge every time you use a normal attack with Diluc. This means you’ll be able to keep a hydro aura on the enemy as long as you weave in a normal attack between each of your elemental skills. Because Diluc’s normal attack has an ICD, some of his normal attacks will not vaporize, BUT most still will, and all of his uses of his Elemental Skill will also vaporize, as those have no ICD. This will SIGNIFICANTLY increase the damage you do, and is the main reason Diluc is considered to be one of the strongest carries in the game. Without this interaction, his damage is much closer to other strong carries like Keqing and Razor, but with it, he just skyrockets above the rest.
Showcase of how much the Diluc+XQ combo vaporizes, thanks to a friend's Diluc because I'm not bourgeois : https://streamable.com/xfj46n
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Gauge with Ganyu

With Ganyu, this is done by using Xiangling. Since both her Frostbloom arrow and the explosion are 1U, you can melt both with Xiangling’s 1U burst or skill. Just use Xiangling’s burst and then switch to Ganyu, and basically everything will melt. This is the HIGHEST theoretical DPS out of all the carries we currently have, but is not always better than other alternatives because of how hard it is to properly play and set up.
Ganyu's damage without artifacts by herself : https://streamable.com/fwpbqk
Ganyu's damage without artifacts with Xiangling : https://streamable.com/c7zb0r
You can see both the initial hit AND the bloom deal more damage, so even if Melt only shows up once, both parts are melting.
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Gauge with Tartaglia (Childe)

Because of the gauge interactions with weak-side melt and vaporize, while they are weaker than strong-side for single instances of damage and impressive crits on abyss 7, most theorycrafters consider them to be stronger than strong-side for consistent team DPS. However, that does NOT mean you should step away from using pyro supports with hydro carries, or cryo supports with Pyro carries. What it DOES mean, is that, when doing this, you should keep in mind that THOSE units are going to be the ones triggering the reactions, so they won’t enable your carry to do more damage, they will BE enabled by your carry, and deal a lot of damage.
The team comp that makes the best use of this mechanic is a Childe team comp, where Childe is the on-field carry, while Xiangling is the enabled support. Since Childe’s Normal attacks and riptide slash have separate and short ICDs, it is unrealistic to use a pyro unit to vaporize childe’s DPS. However, you can use Childe to vaporize Xiangling’s Burst damage. Since Xiangling’s Burst has no ICD, by using her burst and then switching to Childe, you’ll be able to vaporize every single instance of damage she deals, for a significant damage upgrade if you’ve invested into your Xiangling.
WoW cHiLdE oP hE cAn KiLl CrYo PlAnT aT lEvEl 2 : https://streamable.com/5su8ii
A late-game combo for this comp would be done by using Albedo and Bennett. You set up your buffs with Albedo and Bennett’s bursts, then use Xiangling’s burst. After that, you vaporize Childe’s Burst with the initial pyro aura, and then instantly use Childe’s skill and attack the enemy, to start vaporizing Xiangling’s burst. This makes great use of the knowledge we have of elemental gauges, to increase your team’s overall damage output by exactly a metric fuckton.
The combo in action without artifacts, because using artifacts, enemies get 1 shot too fast : https://streamable.com/7lelag
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"Gauge" with Bennett

There is currently only one real exception that I know of that actual makes use of strong-side reactions in the late game, and that is the Bennett comp. Since most of Bennett’s damage comes form his burst and his skill, you want to build pyro damage on him. However, since his normal attacks don’t apply pyro, your applications of pyro will be quite slow. This enables the use of a cryo support, since your pyro applications will never happen fast enough for your cryo applications not to be able to keep up. In order to make good use of this, you need a cryo support that has near 100% uptime on his cryo application, so the best option is definitely Chongyun. Ganyu can also work, but you will have some downtime so I don’t recommend it.
You wouldn't think I have 70% CRIT Rate watching this clip, RNG pls : https://streamable.com/2pdubl
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Gauge with Klee

Klee, unlike Diluc, has more different sources of pyro applications, and some 2U talents. This means it’s much harder to consistently vaporize everything she does. Because of this, while Xingqiu is definitely still an amazing option, he isn’t head and shoulders above the rest as is the case in Diluc comps. Since Mona’s Hydro application is quite slow, she’s not as strong as Xingqiu in Diluc comps, but Xingqiu doesn’t have that edge in Klee comps, making Mona an amazing option in Klee comps.
Klee+Mona, courtesy of yet another friend : https://streamable.com/8btpqt
Klee+Xingqiu, courtesy of that same friend : https://streamable.com/gtbq0m
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Gauge with Xiangling

The last comp I want to talk about for multiplicative reactions is a comp that doesn’t actually have a main DPS. The on-field carry, Bennett, isn’t really dealing much damage in this comp, and is best to run with 4p Noblesse or 4p Instructor. The comp relies on Xiangling and Xingqiu working very similarly to the Childe comp I mentioned earlier. However, this comp allows you to generate a lot more pyro particles, more or less eliminating the need for energy recharge on Xiangling, and letting you build her with only damage in mind.
The reason this works is that you can use your skill on Bennett, and then change to Xiangling to catch the particles. You simply do this over and over until your burst is back up. There are many options for a 4th unit. You can use Albedo for the elemental mastery he provides, post-buff Zhongli to shred resistances, an anemo support for the same reason, Kaeya or Ganyu to convert some of the vaporizes to melts, although this variation can be harder to play properly, or Ningguang for the Petra bonus and the Thrilling Tales.
Xiangling’s burst deals damage based on her stats at the moment of casting, meaning even if Bennett’s ATK buff expires, Xiangling is still going to benefit from it. This also applies to the Instructor and Noblesse bonuses, the Thrilling Tales bonus, and Albedo’s bonus elemental mastery. This comp is not very strong in the current floor 12, because it has no real way to deal with shields, but it has very high damage potential so it might be worth considering.
I love the cryo domain, having enemies that take more than 2s to kill in the overworld is a godsend for testing : https://streamable.com/y3oy04 (I gave up on the mage because I was lazy)
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Other reactions

As I mentioned earlier, Electro-charged is more complicated so I'll address it another day. Frozen has no real gauge applications as far as I know, since comps that include frozen are basically only perma-freeze comps, that don't trigger any other reactions. This leaves us with Swirl and Crystallize
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Gauge in Swirl and Crystallize

Swirl and Crystallize both work VERY similarly to the other transformative reactions. However, much like weak-side multiplicative reactions, the amount of gauge units these reactions subtract is halved. This means a 1U anemo or geo talent will reduce gauge by only 0.5U, and a 2U anemo or geo talent will reduce gauge by 1U.
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Gauge with Ningguang, Sucrose and... Xiao??

You might think that, since swirl and crystallize are both transformative reactions, gauge knowledge isn’t very useful for anemo and geo units, but that actually isn’t the case. Since swirl and crystallize work like weak-side reactions, this means it is much harder for them to remove an aura. This can be insanely useful when choosing artifact sets, as both the Geo and the Anemo artifact sets are tailored to supports. If you have an anemo or a geo DPS, you can consider using a 4-piece set of Thundersoother or Lavawalker, as it’ll be easier to keep the aura on enemies. On top of that, Fischl’s ascension 4 passive actually significantly improves her electro application, as it will apply electro whenever you trigger an electro-related reaction. It has an ICD, so it won’t ALWAYS reapply it, but it’s still quite useful. This means, when using Ningguang or Sucrose, you can actually keep your uptime on thundersoother with fischl or lavawalker with Xiangling close to 100%. This ALSO means those sets might just be one of the options for building upcoming anemo or geo characters, like Xiao.
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Decay Rate + Aura Extension

That’s about it when it comes to practical uses of gauge. Here’s a quick summary of concepts that currently have no good practical uses but that might have some in the future.
1U, 2U and 4U auras decay at different speeds, where 1U takes 9.5 seconds per unit, 2U takes 6 seconds per unit and 4u takes 4.2 seconds per unit. If you use two different talents of the same element, you can cheat these timers, since only the decay rate of the first application stays, while the amount of units is that of the second aura. If you use a 1U followed by a 4U aura, such as Lisa’s normal attack followed by Beidou’s Burst, you’ll be able to make the aura last 38 seconds (4 units x 9.5 seconds). However, since the only 4U aura we can apply at the moment is electro, this doesn’t have practical late-game uses. If you use a 1U followed by a 2U aura, you’ll have a bit more time to trigger your reactions (2 units x 9.5 seconds for 19 seconds instead of 12 seconds), but the increase isn’t big enough to justify using it.
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Conclusion

I'm torn between just hoping everyone enjoyed the guide and finds it useful and wanting to say fuck you to the people who shat on my previous post. Anyways, hope you guys enjoyed, and if, like me, you think text guides are a fucking terrible way to explain something and you still have questions, I explain it much better, with useful background footage, in the video.
https://www.youtube.com/watch?v=mMIa5aEBbVg