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 the mobile version, if a world is saved in hardmode Toxic Sludge will spawn in all worlds on the system.