Internal Cooldown (ICD) is a Gauge Unit Theory mechanism that regulates how often one can apply elemental reactions (and how often one can apply an elemental aura to a target).
For most characters, the default ICD is 2.5 seconds or 3 hits. This means that the ICD is reset either after 2.5 seconds have passed or after 3 hits of the particular move are made. Note:
- Finishing the 3-hit sequence before the timer does not reset the 2.5 second timer.
- The first hit after the timer will apply the element, reset the timer, and reset the hit sequence.
Some characters may have different ICDs for different talents, whereas some character talents may have no ICD at all.
For example, in Yoimiya's Normal Attack sequence, she will shoot 7 arrows over the course of around 2.5 seconds, and she can infuse her attacks with Pyro by casting her Elemental Skill. When she attacks a Cryo Hypostasis, which will have a permanent Cryo aura, because of the ICD, not every shot will trigger a Melt reaction: only the 1st, 4th, and 7th will trigger Melt, as per the 3-hit rule.
Note that the 1st Melt shot will start the ICD 2.5 second timer. The 2nd and 3rd shots do not melt because they were made in less than 2.5 seconds since the 1st shot. Although the 4th shot was also within the 2.5 second window, it melts because of the 3 hit rule (it is the third hit made after the 1st shot).
Moreover, after the 2.5 second timer expires, the next shot Yoimiya makes will Melt, regardless of where in the 3-hit attack sequence Yoimiya is, and start a new 2.5 second timer.
Sometimes a notation is used to represent which hits apply an element (a Gauge Sequence). For example, for Yoimiya's 7-hit combo described above, the Gauge Sequence is: 1 0 0 1 0 0 1. The 1st, 4th, and 7th shots apply Pyro (and trigger Melt), whereas the other shots do not.
Another possible sequence is: 1 0 0 1 0 1 0 0. This means that the 1st, 4th, and 6th hits apply the element. This can happen if the 6th hit occurs after the 2.5 second timer, which will then reset the timer and hit sequence.
See Internal Cooldown/Data for more details.
Note that in general:
- Different characters have different ICDs (i.e. ICD is not shared between different players)
- A single character can have different ICDs for different talents
- Different enemies have different ICDs (i.e. if there are multiple enemies, one can melt or vaporize separately on different enemies, and each enemy will have its own separate ICD associated with it)
- For most characters, the ICDs for Normal Attacks, Charged Attacks, Plunging Attacks, Elemental Skills, and Elemental Bursts are different.
- For most Catalyst and Polearm users, the ICD for Normal and Charged Attacks are separate.
- Exception: For Xiao, the ICDs for Normal and Charged Attacks are shared.
- For most Claymore and Sword users, the ICD for Normal and Charged Attacks are shared.
- Exception: For Kamisato Ayaka, the ICDs for Normal and Charged Attacks are separate.
- Plunging Attacks apparently do not have an ICD.
- The ICD for bow users' charged shots varies between specific characters.
The following is a list of some examples and exceptions to the 3 hit/2.5 second ICD.
- Diluc's Elemental Skill has no ICD, meaning he can Melt or Vaporize each time he casts his skill (3 times).
- Polearm users (except Xiao) have a 0.5 second ICD reset timer for Charged Attacks (different from the 2.5 second ICD). For example, this means that Hu Tao can effectively Melt or Vaporize each time she uses her Charged Attack (considering the animation usually lasts longer than 0.5 seconds).
- Xiangling's Pyronado has no ICD.
- Amber's charged shot has a 1-second ICD reset timer.
- The elemental damage done by Venti's Elemental Burst has a 1-second ICD reset timer.
- Ganyu's 2nd level charged shot and its Frostflake Bloom apparently have no ICD, meaning she can Melt with both the charged shot and bloom damage each time she fires it.
- Xiao's Elemental Skill has a 0.1 second/7 hit ICD rule, meaning that every 0.1 seconds (or every 7 hits), he can apply Anemo with his Elemental Skill (this could be for Xiao's Constellation 6, which allows him to cast his skill while ignoring cooldown).
- As Plunging Attacks apparently have no ICD, every time Xiao plunge attacks, he can apply Anemo to enemies within the AoE. Similarly, Kazuha (with either Constellation 1 or via other cooldown reduction methods) can apply Anemo with his Plunging Attack Midare Ranzan on each use.
- Several of Fischl's abilities, including her Elemental Skill, follow a 4 hit rule (instead of the typical 3 hit rule).
- Diluc's Elemental Burst Dawn follows a 5 hit rule (the Phoenix can hit enemies multiple times rapidly over its duration).
- Tartaglia's Riptide (which hits 3 times each time it is triggered) also follows the default 3 hit rule, but has a separate ICD from his other Hydro attacks.
- Kokomi's Bake-Kurage has no ICD.
- The ICD mechanism also applies to breaking the shields of Abyss Heralds and Abyss Lectors. Because of the ICD on charged shots for most bow characters, Diona may not be able to apply Frozen each time she charge-shots a Herald's Hydro shield. However, one can use Chongyun's Elemental Skill to give a Cryo Elemental Infusion and then switch between multiple sword/polearm characters to apply Cryo to the Herald's shield (since different characters have separate ICDs).