Castle Schwartzvald is the name of the immeasurably large fortress The Dark Lord of Necropolis resides in. The Castle is said to only appear when The Dark Lord expects to have guests.
The Heroes of Arena were sent to the castle by the Outsider during the God War. While entering the Castle the heroes were captured, tortured, and driven to the brink of sanity. After barely escaping with their lives, and not all of their limbs, the Heroes plunged into the dark depths of the tainted citadel. After many painful encounters the heroes devised a plan to escape the planar locked castle via a portal to the elemental plane of ice which was a trap within.
The Heroes were able to successfully open the portal to the elemental plane of ice and create an explosion of incredibly magnitude to take place within the castle as soon as their portal closed. The Atomic Bomb effect caused by their plan was assumed to have killed the majority of the residents and guests of Castle Schwartzvald, and it is assumed that the Castle was destroyed.