Talus

Talus' are custom mobs thats spawn in caves. They resembled large, wide and short golems. They are about as tall as the player, and have high health. When attacking, they'll hit the ground with the arms usually knocking the player back.
A very good tip to fighting these mobs is to use your pickaxe when attacking them instead of your sword. Using your pickaxe will cause massive damage to the talus unlike the sword which takes awhile to kill the talus with.