Astral is a mysterious entity from Astral World who serves as the secondary protagonist of the Yu-Gi-Oh! ZEXAL series.
Astral makes a list of his observations of Yuma and other human behaviors while offering his dueling wisdom to the him in order to obtain the 99 "Numbers" Cards which are actually fragments of his memories which got scattered when he entered Yuma's dimension. He normally resides in a special world within Yuma's Key, featuring a strange ship whose parts become unlocked as Astral collects more "Numbers" cards.