"The mists that shrouded this lake miraculously now cleared away, revealing an ancient citadel. So Moebius had not lied. Or perhaps this was simply another of the Time Streamer's illusions, meant to slow my true endeavor."
The Lake of Tears was the largest inland body of water featured in maps of Nosgoth, first introduced in Blood Omen: Legacy of Kain. Bordered on the west by mountains and situated near the Pillars of Nosgoth, it was the westernmost point that has been encountered in the series. The lake cannot be visited in Blood Omen: Legacy of Kain, but was fed by the waterfall stemming from Nupraptor's Retreat, and the resultant (accessible) river which flowed through and south of Vasserbünde.
While not explicitly identified in Legacy of Kain: Defiance, it is almost certain that the Lake of Tears is the misty expanse which harbored the Vampire Citadel. In the fourth timeline, Moebius instructed Kain to travel west of the Pillars when directing him to the Citadel: the Lake of Tears is the only body of water in this area. Using the Balance Emblem, Kain was able to dispel the mists shrouding the Citadel from view. During the Blood Omen era, Raziel and Janos Audron witnessed the destruction of the Pillars from across the lake, and Kain gazed out solemnly across its moors after battling the Elder God.
In Blood Omen's map, a large sea serpent is depicted within the center of the lake, reminiscent of cartographic "here there be monsters" warnings of early seafaring in the real world. Until the release of Legacy of Kain: Defiance, the warning remained a mystery, and was the root of some fan speculation. The introduction of the Vampire Citadel and the enigmatic mists surrounding it go toward explaining the origin of such a deterrent.
The name "Lake of Tears" may etymologically serve as a reference to the tragedies that befell the Vampire Citadel and its inhabitants, the Ancient Vampires.
The Blood Omen 2 map, which extends further southwest than others, shows that the Lake flows into the Great Southern Sea. However, its proportions are diminished in comparison to other maps. A small expanse of land can be seen within the lake uniquely on the Soul Reaver 2 map.
↑Moebius:"The answers are plain if you know where to look. Go west of the Pillars - there you will find a testament written in stone.." Crystal Dynamics. Legacy of Kain: Defiance. (Eidos Interactive). PlayStation 2. (November 11, 2003) Transcript.