Peaca Dungeon is a subterranean crypt located in northwestern Sen Mag Prairie. It teems with undead monsters, most of which are powerful and have advanced skills such as Chain Casting. According to Aodhan, the source of the Peaca monsters's power come from Another World.
- It is said by some Peaca dungeon's creation is due to the Second Battle of Mag Tuireadh.
- In Irish, peaca (pronounced /pakə/) means sin.