Rainbow Slime

The Rainbow Slime is a rare hardmode monster that spawns in any hallowed biome. It can only spawn while it's raining, or during a blizzard if you're in a hallowed Snow Biome. The Rainbow Slime's color shifts constantly, as do the Rainbow Bricks it drops. They are immune to the Poisoned and Venom debuffs. This is the slime that does the most damage so far.