King Slime

The King Slime is a new mini-boss added in the 1.0.4 patch. As the King Slime takes damage, it slowly spawns additional slimes and also becomes smaller until defeated. The King Slime is considered a subspecies of Slimes in general because it uses the same AI and similar graphics.

Spawning
The King Slime appears to spawn completely at random. It has been seen both above and below ground, during night and day. There are no known criteria needed for King Slime to spawn. It seems that the King Slime targets a single player on the server, and if that player is killed, the mini-boss disappears, unless other players are in immediate view.

Being very far away from the spawn and possibly holding a water candle may help in spawning it.

As of the 1.1 patch, the Slime Crown is needed to summon the King Slime.

Strategy
The King Slime behaves exactly like a normal slime (it uses the slime ai), except that it spawns other slimes after being hurt by the player. Due to its predictable nature, it is easy for a new player to defeat the mini-boss with even lower tier weapons. The only thing a new player should worry about is dodging the King Slime as it jumps about, as this could become a nasty fight very quickly. To finish the mini-boss quickly, projectiles such as Shurikens or Arrow (Which you use with Bows) are recommended. He can note as normal Boss.

Drops

 * 1 Piece of Ninja Gear: 99.99% (9999:10000 chance)
 * Ninja Hood: 33.33% (1:3 chance)
 * Ninja Shirt: 33.33% (1:3 chance)
 * Ninja Pants: 33.33% (1:3 chance)

Trivia

 * If you look closely enough, you can see that there is a ninja inside the King Slime.
 * This would explain why you get ninja clothes when you defeat it.