By plunging the Water Reaver into a waterfall, Raziel could magically freeze the cascade, and scale the ice to ascend to the upper level. However, the ice always thawed back to flowing water after a few seconds, and needed to be frozen again in order to be climbed.[Defiance]
Behind the scenes[]
The Water Reaver was originally designed for Legacy of Kain: Soul Reaver, but was cut from the final product. PSM reported that the Wraith Blade would have been "imbued with water by passing it through running water (e.g., fountains, spouts, waterfalls)."[1]
Another incarnation of the Water Reaver was excised from Soul Reaver 2, which may itself have been employed in conjunction with that game's waterfalls.[2]