Star of Darkness Castle
Seireiden reboot
Name in Japanese星黎殿
Rōmaji TranslationSeireiden
Appears InAnime, Light Novels
Known UsersBal Masqué
Technical Details
Related Treasure ToolsTendōkyū
Triggers Unrestricted Spells


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.


A unique feature of this floating mass of land is that the sky around it is a perpetual nighttime full of stars. This contrasts with Tendōkyū, which displays eternal daytime.

X1 Seireiden and Tendoukyuu

The link that connect the twin fortresses

Unbeknownst to Bal Masqué, Gavida did not tell them that a hidden feature of Seireiden and Tendōkyū was that they were linked, and if one of the floating fortresses were brought close enough to the other, a bridge would be created between them, allowing a surprise invasion and rendering the Crypta useless. Wilhelmina Carmel's knowledge of this fact allowed her to ultimately invade it during the Second Great War with Khamsin Nbh'w and Rebecca Reed, revealing its location to the Flame Haze Army.


After the battle, the castle was moved to Misaki City, and the Snake of the Festival had it transformed into the tower-like Saishuku no Shadan by Dantalion to be used for the Grand Order in the creation of Xanadu. The tower was once on the brink of collapse because Khamsin had destroyed its foundation. Sydonay threw his enlarged spear directly through the tower, supporting it from crumbling down.


After fulfilling its duty, the tower was divided into several parts by Bel Peol through Trivia. Leaving the extra parts from Dantalion's work, she brought only the original parts of Seireiden with her to Xanadu. Like its counterpart Tendōkyū, Seireiden has the ability to gradually rebuild itself; it took about two years, the same amount of time Tendōkyū used, to return to its original form. Later, it functioned as Bal Masqué's headquarters once again.


  • The name 星黎殿 (Seireiden) literally means the Palace of Stars.



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