Corvus is a ruined city that lies beneath the Blood Marsh.
Corvus was one of the first cities of Sanctuary, established by the nephalem, and one of Sanctuary's greatest civilizations. Passages in the Books of Kalan indicate that the city was built by Daedessa the Builder. Lidar the Noble infused the city with some form of magic that could ward off trespassing angels and demons. After Inarius altered the Worldstone to stymie the nephalem's abilities, the nephalem became mortal, and forgot their past heritage. Thus Corvus was forgotten and left to come to ruin. Powerful defenses left behind by its nephalem inhabitants deterred most adventurers from finding the city.
Millennia later, Rakkis, having heard of the existance of the nephalem and Corvus, established Westmarch near where Corvus was said to lie. Obsessed with the nephalem and the power they held, it was his ambition to locate Corvus. He succeeded in locating the city, and took the Wolf of Corvus as the sigil for his new kingdom. The lure of potential immortality convinced Rakkis that he might even be nephalem himself, though after many fruitless years of wandering the crumbling remnants of the city, his only consolation was to have his remains entombed within.
It is said that at the age of 100, Rakkis died peacefully in his sleep. In his final years, Rakkis requested that he be buried among the ruins of the lost city. This was apparently granted, and Rakkis was entombed in the heart of Corvus.