Debuff
Infest
Whenever an enemy under an Infest debuff dies, deals pure damage to all other alive enemies. This pure damage is equal to 50% of the enemy's MAX HP who died while under the Infest debuff. This pure damage cannot be critical. The pure damage dealt upon killing a Boss or their minions cannot exceed more than 10% of their MAX HP.
What the game's own status effects screen says
In the game data this effect appears as Infest.
Champions that apply it
1 champion have a skill that applies Infest, according to the effect lines in the game data. This lists who applies it, not how reliably: chance, duration and resistance are on each champion's page.
The description is the game's own text. It has not been tested in battle here, and the game's wording can be loose (for example about numbers that differ between versions of an effect). See Data quality for what has and has not been checked. Found a mistake? Use "Report a problem" at the bottom of the page.