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

 * Toxic Sludge and Pinky are the only two members of the Slime family not to have the word "slime" in their name.
 * Its appearence could be a reference to the pokemon Grimer.