Vex

The Vex is a mob added in 1.11 that is spawned by the Evoker.

Behavior
Vexes are hostile mobs that attack the player and villagers. Vexes can float through walls, and will attack villagers as commanded by the Evoker. When attacking, you can see a texture that makes it's front side red. If summon by an Evoker, Vexes will take damage after a certain amount of time. This does not apply if summon by spawn eggs or with /summon.