Emperor's Key

The Emperor's Key (Ō no Kagi) is a necklace belonging to Yuma Tsukumo.

The Emperor's Key is a mysterious artifact given to Yuma by his mother. It's the one that allows Yuma to bring Astral forth. It is desired by Kaito Tenjo. Astral can supposedly go into the Key and see the large structure seen in the first opening.

Trivia

 * It is possible that this key has something to do with Yuma Tsukumo's Number card, "No. 39 Aspiring Emperor Hope", due to the key having the same color as it, and "Emperor" being in both their names.


 * There is an unknown structure within the key that may have something to do with Astral.


 * The structure in the key is the second structure to have appeared in an alternate dimension, the first being Divine Temple from Yu-Gi-Oh! 5D's.


 * The artifact also bears a resemblance to the Millenium items from the first series of Yu-Gi-Oh. A connection has yet to be established however.