Toxic Sludge

The Toxic Sludge is a Hardmode Slime Enemy that appears in the Underground in place of ordinary Slimes. They deal significantly increased damage and have a 50% chance of inflicting the Poisoned Debuff, which they are also immune to.

Trivia

 * The Toxic Sludge is one of the few enemies in Terraria to have a visible smile, the others being Snow Balla and Snowman Gangsta.
 * Disregarding the Gastropod, it is the only slime on which a face is visible.
 * The Toxic Sludge seems to replace the Mother Slime

History
毒泥 Токсичная муть Boue Toxique