Shadow Palace

The Shadow Palace (影の王宮) is the magical space between the realm of the living and the realm of the dead.

Description
The Shadow Palace is a large black structure shaped like a castle. This magical space serves as a gateway from the realm of the living to the realm of the dead. It exists within Clover Castle, the capital of Clover Kingdom. The internal structure of the palace is shaped like a giant sephirot, with ten spherical rooms connected by corridors. The walls and floors are made of stone blocks, and the vertical corridors have floating blocks to facilitate travel. After Yuno's magic stone enters the palace, an eleventh room forms with the large pedestal for the stone, which will complete the elves' reincarnation.

The ancient elves allowed humans to safeguard the magical space, but only the ten Apostles of Sephirah can open it.

Trivia

 * The internal layout of the Shadow Palace, as well as the name "Sephirah" from the Apostles of Sephirah, are derived from the Sefirot in Judaism.