Vindicator

Vindicators are hostile mobs, and one of the two "Illagers", the other being the evoker.

Through natural generation
Vindicators spawn inside naturally generated woodland mansions in groups of 2–3, alongside evokers and other hostile mobs.

Some rooms in the mansions are forced to spawn 1-2 vindicators.

Drops
Vindicators only drop loot on player kills. They have a 15% chance to drop an undamaged iron axe, increased by 6.25 percentage points per level of Looting. They will also drop 0–1 emeralds, with the maximum increasing by 1 for every level of Looting.

Behavior
Vindicators are hostile to both players and villagers. They will try to attack them with an iron axe, similar to a zombie's attack. When in pursuit of their target they will sprint toward them. When not attacking, they don't have the axe in their hand.

If a Vindicator is named "Johnny", it will be hostile to any kind of mob, except for evokers and other vindicators.

Data values
Vindicators have entity data associated with them that contain various properties of the mob. Their entity ID is.

The iron axe they hold is not part of their NBT; in general, a vindicator does not display any armor items or held items from its NBT.

Trivia

 * Naming a vindicator "Johnny" causing it to attack anything in sight with its axe, is likely a reference to Stanley Kubrick's The Shining, specifically the famous scene wherein Jack Nicholson smashes a door with an axe and says "Here's Johnny!"