When an island is spawned, it comes with a considerable amount of bosses, each located in a corresponding Setpiece (a fixed shape part of the map, shows as a red square in the minimap). If all of the high-level Setpiece bosses are killed, everyone who was on the island gets sent to the final boss, who is as deadly as she is rewarding. Bosses weaker than Doctor Octo are not needed to close the realm, and will actually respawn if nobody is around the Setpiece area for around 10 minutes. Also, killing high-level Setpiece bosses gives a chance to spawn a random Event boss.
In order to qualify for loot from any boss, players must deal damage equal to at least 0.3% of the boss's unscaled HP.
- The Bomb Maker (Bomb Factory)
- Lazer, the Victorious (Laser Playground)
- Commodus (The Arena)
- Dr. Geckelston (Home for Special Children)
- High Priestess Tiffany (Temple of Bast)
- Traitor Phoenix (Reeducation Camp)
- Poison God (Venom Compound)
- SN-Z (Iron Lair)
- The Frozen Horror (Frozen Owl Monastery)
- Dark Sphinx (The Elder Arena)