Evoker

The Evoker is a mob added to 1.11 and is one of the two "Illagers", the other being the Vindicator.

Natural Generation
Evokers spawn inside naturally generated woodland mansions in groups of 1, alongside vindicators and other hostile mobs.

Drops
Evokers will always drop 1 Totem of Undying, as well as 0-1 emeralds.

Behavior
The evoker will attack the player or villagers, similar to zombies.

Bite-like attack
One of the two forms of attacking the evoker uses is summoning a dozen alligator-like entities out of the ground. When threatened, the evoker ascends many of these 'alligators' in a horizontal line toward the player or a villager. These 'alligators' bite consecutively after the last one, until the attack finishes. These bites deal of damage, regardless of armor or enchantments.

Vex Summoning
The other attack the evoker uses is to summon 3 vexes per attack when threatened.
 * The evoker will continually summon vexes, even when there are some still alive from the last summoning.