Casthys is a large city within the Ashfall Isles and serves as the capital of the Lunar Zolá Protectorate. A free city for many centuries, it was fought over by its natives and the Lunarians for decades during the Lunar Ashfall War. The Lunar name for the city is Casthysk, which was a slavicization of its earlier anglicized name of Casthys which was already a corruption of its original native name of Kaasthika.

The city houses the underground Ashpits, infamous for their deathbattles that invite gamblers, fighters, and spectators from all across the world.