Debuff
Nullify
Champions under the Nullify debuff cannot have their skills activated, participate in Ally Attacks, be granted an Extra Turn (except via Metamorph) or an Instant Turn, have their skills' cooldowns decreased, have their Shield's value increased, have their destroyed HP restored, have their HP swapped by allies or by themselves, Evade enemy effects or skills, have their Turn Meter equalized, or have their HP balanced.
What the game's own status effects screen says
In the game data this effect appears as Nullifier.
Champions that apply it
1 champion have a skill that applies Nullify, 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.