Hainkyall is a powerful Outsider, known also as the Corruptor, The Defiler or Faustophelese. He is responsible for the dissemination of ancient knowledge about the Old Ones into the world. To do this in a subversive manner, he often selects those individuals already possessing questionable morals, especially those that have already performed some immoral act that has not yet been discovered.
Because of this, he generally targets scholars seeking forbidden knowledge, clergy flirting with dark powers, Thaumaturgists looking to expand they power or life span, or those possessing other monstrous secrets.
Hainkyall is one of the most tolerable of all the Outsiders to look at, primarily because he chooses to appear as a human being, although often one possessing some sort of disconcerting physical flaw. He often assumes the appearance of a puritan preacher, or minister- but has on occasion taken other forms.
Ancient Tomes indicate he can change his appearance at will, erase memories and even entire personalities as desired. He can become invisible at will, and can selectively allow himself to be seen only by those he chooses when he chooses.
He is also said to be able to dispel any ritualistic ward that he desires, provided the ward is created by a creature less powerful than himself.
In 1936, this Outsider made an appearance at the Library of Esoteric Studies, where he spoke at length with Agostino Selletti with whom he had a prior arrangement. In return for not destroying the SAVE Envoys there, he was granted a powerful artifact.
While not all the conditions of the arrangement between Selletti and Hainkyall are known, it is apparent that the Outsider has agreed to protect the uncorrupted corpse of the cardinal to the point of murdering anyone that discovers Selletti’s secret.