When Ath Velanis was built, it was used by Malgorthios the Black in order to sacrifice women screaming to the Old Gods.
Centuries later, this fortress housed madmen, demons and the Fraternity of the Grinning Abomination.
Eventually, it fell into ruin until Aurelian Titus chose it as his headquarters. In addition to its strategic value, the fortress also serves as a place where prisoners are held as well where magical experiments take place.
This section contains spoilers for: Dragon Age: Until We Sleep.
The plot follows BioWare's own canon, meaning that Alistair is king of Ferelden in the comic's story.