Ospawns are penance that have a 1/1,000 chance to be spawned instead of standard king spawn during the fight with the Penance King in the final wave of Barbarian Assault hard mode. They function identically to standard king spawn, possessing only a different name and examine text.
If they touch the player, they explode and deal 25% of maximum health as damage in an area. If one is killed when a player is near it, the same damage is dealt. Due to their high explosion damage and very low health, it is recommended for players to take them out at range. Resonance will block but not heal from their explosion. Ospawns will eventually explode on their own if not killed quickly enough.