The title of this article is conjectural. It might not be used by any official media related to the article's subject.
The Astral Tower is the central structure in the Astral World. From within its walls, Eliphas rules the world. At the top is a room with ornate pillars and it its center is a throne, which features a larger version of the Emperor's Key on top.
After Astral was forced to retreat to the Astral World due to the injuries he sustained from Number 96, Eliphas placed him in an Astralite stasis crystal atop the throne until he was prepared to overwrite his memories. Yuma Tsukumo eventually arrived in the Astral World to rescue Astral. Despite Eliphas' intervention, Yuma eventually reached the tower with the assistance of Rainbow Kuriboh and Enna. Here, Eliphas confronted him and they began a Duel to decide Astral's fate.
The denizens of the Astral World were able to witness the Duel in the tower through Astralite crystal viewscreens. When Yuma eventually defeated Eliphas, he was taken to the tower's balcony, where Eliphas realized that the Barian World was making its move due to Don Thousand's release. From here, he returned the ZEXAL wielders back to the Human World.