This monster, as of late, spawns in a lot of different places. Just go into the Hall of Magi ( 80, 25, -44 ) /waypoint 80, 25, -44 and all the mobs in that room are PH's for this mob. Meanwhile, one spawns outside the instance entrance inside Crushbone Keep (Level 2).
War and Wardrobe - Although this monster is not a Named, they are required for a step of this quest. If none are up, clear the room. Every mob in this room shares spawn points, so kill everything to spawn more clerics (approx. 12 minute for respawns).