Aoskar, the Keeper of Gateways, was an ancient god of portals and planar travel, popular enough among Planewalkers to make him one of the greater Powers. In a deliberate attempt to take over Sigil for himself, he encouraged his followers to spread his faith there. He surged in popularity until every step through a door became an opportunity to pray to Aoskar, and the use of portal keys became inseparable from his rituals. Eventually he became the unofficial patron of the City of Doors, and even the Dabus began to worship the deity. Finally, one of the dabus, Fell, even became Aoskar's priest. The folk of Sigil began, chant says, worshiping the Lady of Pain herself as Aoskar's mere aspect.
The Lady killed the power for his troubles, casting him out of her city and into the Astral Plane where the corpses of all dead gods drift like stony islands in the void. His great temple in Sigil was shattered; later on, its ruins were taken over by the Athar by way of making a point about the mortality of powers.
His worship is now illegal in Sigil; the authorities don't want to risk offending the Lady of Pain again. Some remnant of Aoskar's heritage exists through Aoskian Hounds. The few remaining followers of the Keeper of Doorways are few, and nervous, but is said they know the secrets of portals even the Fraternity of Order doesn't know about, and that the blood of their deity, which resembles wine, can act as the key to any portal, lock, or gate. But Aoskar himself is nearly forgotten by most.
In life, Aoskar was true neutral in alignment. His portfolio included portals, doorways, and opportunity.
Imendor was his last priest.