The Mansion

From fattwiki

The Mansion was an elaborate mansion in the woods of Hieron, located between Marielda and the plains. It was once the home of Samothes, Samot and their child Maelgwyn, a gift to them from Samol meant to serve as a memento after his death. While Samol hoped it would bring Samothes and Samot together, it actually ended up being the site of their separation.

Hitchcock's mother, when she was a little girl living in the plainlands, would go play with Maelwgyn in the mansion "where the richest family in the world lived". Over the course of Marielda, Hitchcock seeks the other half of a map to the mansion. Both Edmund and Aubrey have visions where they see the mansion and its inhabitants.