These are all default registry entries of this type.
This registry is modify-able through datapacks.
mob
mmorpg:arcane_spider
mmorpg:nature_zombie
other
mmorpg:water_mage
mmorpg:fire_mage
mmorpg:nature_slime
mmorpg:water_chicken
mmorpg:thunder_zombie
mmorpg:water_spider
mmorpg:boss_golem
mmorpg:fire_chicken
mmorpg:nature_chicken
mmorpg:arcane_zombie
minecraft:wither
player
npc
mmorpg:thunder_slime
mmorpg:fire_skeleton
mmorpg:nature_skeleton
mmorpg:healer_mage
mmorpg:nature_spider
mmorpg:thunder_spider
mmorpg:water_zombie
mmorpg:arcane_slime
mmorpg:water_slime
minecraft:pig
mmorpg:thunder_skeleton
mmorpg:fire_zombie
mmorpg:water_skeleton
mmorpg:fire_spider
mmorpg:fire_slime
animal
mmorpg:thunder_chicken
lycanite_mobs
mmorpg:nature_mage
mmorpg:thunder_mage