Source: The Infernal Syndrome, pg(s). 66
The wizard Sheel Leroung was an politcal ally of the founder of the Hellknights, Daidian Ruel, and beginning in 4581 AR aided in his research into the afterlife and the organization of Hell's legions. In 4599 AR he was given permission by Lictor Aligois Thels to take 20 Hellknights into the western edge of the Menador Mountains on a private venture. In return for this, Leroung provided funds to create a new Hellknight fortress there: Citadel Enferac.