While Hastur is best known as part of the Cthulhu Mythos, he was originally created by Ambrose Bierce in the short story "Haita The Shepherd". He later appeared in one work by HP Lovecraft, but is best known for his role in August Derleth's stories. Hastur is the half-brother of Cthulhu.
He is also known in other names:
The Feaster from Afar, a black, shriveled, flying monstrosity with tentacles tipped with razor-sharp talons that can pierce a victim's skull and siphon out the brain
The King in Yellow
He Who Is Not To Be Named as saying Hastur's name three times in a row (Hastur Hastur Hastur) brings the chanter death.
The King In Yellow is also the title of a book (and a book within that book) where Hastur is mentioned. The name of his material card, as well as how it must be acquired, are references to these last two names.
Hastur appears as a Persona in Persona 2: Eternal Punishment. He may not differ from the others gameplay-wise, however, he stands out since his material card, The King in Yellow, cannot be acquired by normal means. To get it, the player must talk to the Wang Long-obsessed girl in 2X Slash, located in Aoba, and say "HASTURCOMEFORTH" (イ ア イ ア ハ ス タ ア) as their birth month when prompted. After that, Hastur's material card will be found in a package by Maya Amano's desk, in Kismet Publishing.