Castle Glas is a setting in the Metal Shadow universe. It is a castle located deep in the Mu Ganaelyn mountain range. Its westernmost wing houses a chamber where royalty can get together for meetings. This is where king Rula and queen Rula first learned of the Red Threat, and where the Red Threat, nine years later, learned of the prophecy of nine.
Detailed descriptions of the castle were not given in Metal Shadow. It had a town surrounding it which was destroyed by the Red Threat.