Windemere

Windemere, northeast of the Dry Lands... a place of darkness. Built on a island in the icy sea, this fortress was a the keep of the dark sorceress Elistaria, who was very high up in the Oppression of Lord Blackthorn, mastering the darkest arts to strengthen the dictatorship. Daemons guarded the castle and its inhabitants were the darkest people imaginable. The Avatar visited this dark place in Ultima V to get the Black Badge and then leave as fast as possible.

The darkness of the place turned out to be its doom, for when the Underworld started to collapse, the dark forces of Windemere amplified the destruction in the area, and the island was totally destroyed.

Windemere in Lazarus
In the Lazarus version, Windemere was once the keep of a member of the Great Council. Also, Elistaria used it to train dark mages for the Oppression. Beside the Daemons, Skeletons also guarded the keep.