Possessed Armor

The Possessed Armor is an enemy that was added in the 1.1 update. It can be found in all biomes during the night, even underground. These enemies are much more powerful than your average Zombie, and are a very large threat to your NPCs, particularly during a Blood Moon, where they have the same ability as zombies to open doors that are not otherwise reinforced.

The Possessed Armor is shown in the 1.1 trailer, and in a screenshot from Steam.