Spawn /loc -367, 398, 105. The Overseer spawns on the balcony across from the Master of the Guard. The Overseer spawns after killing all mobs along the balcony NOT including the Master of the Guard. All mobs below the balcony do not need to be killed to trigger the spawn. All mobs behind doors along the balcony do not need to be killed to trigger the spawn.
It shows up in spell search and in the real-time drop-down results from the site-wide quick search, but not on the results page of the quick search, itself (actually the spells tab appears to be absent from that results page altogether).