Silverbirch's Fortress, usually referred to simply as the Fortress, was the castle of King Silverbirch on Whitewings. It was presumably the home of the Whitewings monarchy prior to Silverbirch.


Urchin was brought to the Fortress after being abducted from Mistmantle, and brought into the presence of Silverbirch. He was imprisoned in a cell in the Fortress for some time following his capture.

The Fortress was eventually destroyed in a collapse that occurred as a result of Silverbrich's obsessive silver-mining. It was later replaced by a new royal residence, the House of the Marked Squirrel.