Hastur (アスツァール Asutsāru, "Asthur") is the Partner Z/X of Urara Yato.
Z/X Encyclopedia Entry
Cunning and ruthless. She is an existence that is also called as the reincarnation of "Azathoth"—the Cthulhu born with "malice". She drove the gentle Dingir clan to their downfall on whim in the time immemorial, and is also responsible for turning them into incarnations of grudge.
She is currently charged for her crime and imprisoned for eternity. Her tremendous power has been lost for ages, and her physical appearance has also changed to a childish one. But this doesn't change the fact that she is still a threat.
...Nevertheless, her fetters was about to be removed by a certain person.
