The Blight Slime is a decently uncommon Pre-Hardmode slime that spawns in the Corruption/Crimson biome. It has two variants, which appear depending on the world's evil biome. It drops Blighted Gel, a crafting material used in the crafting of the Overloaded Sludge, which is the summoning item for The Slime God, as well as various other recipes such as the Zen Potion.
Ebonian Blight Slime
Crimulan Blight Slime