Main article: Bosses
King Slime is a giant blue slime with 2,000 health (2,800 in Expert Mode). It is summoned with a Slime Crown, after killing 150 slimes during a Slime Rain, or can also rarely appear in the outer thirds of the map completely by itself. As with all enemies that can spawn naturally, the King Slime has a better chance of spawning while standing near a placed Water Candle or while under the effects of a Battle Potion. King Slime is a good challenge for a beginning player, and can be easily defeated by tactical use of terrain.
On the Desktop version, King Slime gains the ability to teleport to the player if they get out of its reach for too long.
King Slime does not provide access to game-advancing items upon defeat, but outside Expert Mode will drop one Gold Coin, one or two piece(s) of Ninja clothes, and one of several slime-related items.
In Expert Mode, King Slime has much more health and can summon Spiked Slimes, that are similar to the Spiked Jungle Slime and Spiked Ice Slime.