The Thief is a normal creature that will spawn, they are a human.
Speed: 2/3 (Slow)
Damage: 5/15HP (Melee) 15/30HP (Ranged)
They have a ranged attack (Throwing knives), so they move in on the player, until they are close enough, and then they throw their knife and back away and get ready to throw again.
They will also move in a random direction circling the player, and will try to dodge projectiles from the player.
Sometimes a Choppa will spawn with a Thief on it's back, which will drop off if the Choppa dies.