Charmcaster built it when she became ruler of Ledgerdomain. The only room that was shown was a bedroom and the way the doors open. It also has a courtyard where Charmcaster took Darkstar to battle her Rock Creatures and Ben and Kevin.
It was destroyed by Charmcaster's fury when she realized that Darkstar was only using her and never loved her. She has since moved to a bizarre small house elsewhere in Ledgerdomain, as seen in Charmed, I'm Sure.