Wall of Flesh

The Wall of Flesh (WOF) is a new boss located in The Underworld that has been introduced in the 1.1 patch.

After defeating this boss, your world will enter hardmode and you'll be facing tougher enemies.

It possibly licks you with The Tongue as a form of attack, or may drop the The Tongue as an item upon death. It summons worms out of its mouth and shoots lasers out of its eyes. It spawns in The Underworld. It looks like it is made out of left over body parts including 3 fleshy Eye of Cthulhu, which is where many of its attacks appear to be based.