One Hive Spawner spawns in each Hive Nest.
Spawning Hive King
When interacted with while holding a Hive Egg, the Hive Spawner will consume it and spawn Hive King. When spawned in this manner, Hive King starts small and slowly scales up while gaining health, so there is a slight delay before the fight begins.
Note that damaging the Hive King in this phase will cause it to despawn without dropping any items. Avoid interacting with Hive King until it has finished spawning.