Toxic Sludge

The Toxic Sludge is a Hardmode Slime enemy that appears in the Underground layer 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
This Slime is the only slime that bears any kind of facial resemblance.

bugs
In mobile if a world is saved in hardmode these will spawn in all worlds