Slayers

Slayers can be started through an NPC in the hub: Maddox.

There are currently 4 different types of slayers:

Revenant Horror
Spawned by killing a given number of zombies anywhere in skyblock
Tarantula Broodfather
Spawned by killing a given number of spiders anywhere in skyblock
Sven Packmaster
Spawned by killing a given number of wolves in the Hub
Voidgloom Seraph
Spawned by killing a given number of enderman in the End

There are 5 tiers of slayers, each harder than the next. Currently, only Revenany Horrors have a tier 5 boss, in which they are renamed to the Atoned Horror.