Toxic Sludge

The Toxic Sludge is a Hardmode slime enemy that appears in the Underground layer in place of normal slime enemies. They deal a vastly increased damage from normal slimes, and they also have a 50% chance on hit to afflict the player with Poison. They drop gel like the other slimes.

Trivia
This slime is the only slime with a face. This slime, along with Pinky, are the only slimes without "slime" in their name.