It is unclear on how many times she would need to be hit and if Raziel would need to use the Soul Reaver for the final blow.
The Priestess boss battle would have taken inside a tall tower with its foundations in the Undercity.
Raziel´s goal was to eliminate the vampires summoned by the Priestess and climb a wall to get to her. The circular layout of the room potentially hints that she might have teleported around. Consuming her soul would grant Raziel the Possession ability needed for Raziel to enter the smokestack in the north.
The Priestess and her battle are present in the alpha builds of Soul Reaver, however it doesn't function correctly. Instead of appearing on the high balconies the Priestess spawns on the floor of the chamber - making somewhat easy prey. Melchahim Vampires spawn in one at a time but do not appear from behind the doorways intended for their entrances.
... Daniel mentioned that the Priestess battle involved her way up on a ledge, summoning monsters to fight Raziel. ...
... Ok so the Priestess was tied to the Undercity, which was gorgeous.. man I was sad we couldn't get that on PS1. It was a nod to Lebbeus Woods, the famous architect. The Priestess was a mind/spirit controller, so Raz would enter this arena with several doors around him. There would be several gladatorial waves of controlled enemies (humans, worshippers, Dumahim, Melchiahim, etc.)and she would be on this couch at the top. Raz would have to mop up the crew and glide to hit her a few times before he'd be forced back down to deal with the next wave. So yeah, groovy mind powers. ...