The Lake of the Dead

In Soul Reaver, Kain sentenced Raziel "to burn forever in the bowels of the Lake of the Dead". This implied that the Abyss was situated in a lake of that name, and that its waters fed the whirlpool.

The Lake of the Dead could be located on maps of Nosgoth. The in-game map for Blood Omen showed it clearly. It did not contain the Abyss in that era; instead it had an island with a teleporter that took Kain to the Lost City. The lake could be explored by travelling west from the Mist form dungeon and, unless he resorted to Bat form, Kain crossed part of it to reach Vorador's Mansion.

FURTHER OBSERVATIONS

Amy Hennig (director and storywriter of Soul Reaver, Soul Reaver 2 and Defiance) has said there is a connection between the Lost City and the Abyss, but at the current time, there is no indication as to what that link is, except that they appear to share the same location, both being in the Lake of the Dead.¹