Seireiden(星黎殿Seireiden, Star of Darkness Castle) is a massive Treasure Tool that currently serves as the headquarters of the Crimson Realm-based organization Bal Masqué. It was created by Gavida along with its counterpart Tendōkyū. It has a cloaking ability called Crypta, which makes it invisible to detection by any means visual or magical, which Bal Masqué uses to hide its location, as Decarabia mentions it has never been breached.