Elemental reactions are one of the unique mechanisms that every Genshin Impact gamer needs to understand.
However, there are many cases where you attack an opponent with an elemental attack but do not create a reaction and reduce the amount of damage dealt.
What is ICD?
As mentioned above, ICD stands for Internal CoolDown.
After a period of research, the international Genshin Impact community shortened this mechanism to a more understandable rule, the `3-hit rule`.
Another thing gamers need to know is that in most cases, normal and heavy attacks of characters using single swords and heavy swords will share ICD with each other (except for Ayaka).
How to apply ICD?
With the `3 Strike Rule` as mentioned above, Genshin Impact gamers can use spear-wielding characters combined with Chongyun’s elemental skills to be able to destroy the Abyss Apostle’s Water shield or freeze monsters.
Next, with the characters’ ICDs not sharing with each other, you can continuously change characters and apply Fire or Ice signs when in the elemental skill area of Bennett (destiny 6) and Chongyun.
Furthermore, understanding the period of time when elemental signatures cannot be applied from the ICD mechanism will help gamers avoid wasting the characters’ damage.
Conclude
ICD is a hidden mechanism and is not directly explained in the game, so many Genshin Impact players, even though they have been playing for a long time, still do not know about it.
Eliana 
Olivia