The Cult of Bloonarius

The Cult of Bloonarius is a group of evil monkeys and bloons whose main goal is to revive their fallen leader, Golden King Bloonarius. They appear in Bloons: Clash of Worlds in chapters 11 and 12, where they succeed in reviving GKB.

Nightmare Bloon
The leader of the Golden Army. He was almost killed in Bloons Golden Defense, but survived.

Crimson
An evil monkey who is actually Ezili's sister. She ends up betraying GKB and helping the monkeys defeat him.