Confirmed spawn location at very top of stairs in far NW building at 2200 1238 165. Red con to lvl 100. Did not notice anything out of the ordinary, pretty straightforward fight. Has a good amount of HPs. Dropped "Earring of the Eclipse (slot 7 & 3)."
Another confirmed spawn location down stairs at 2151 1288 102. This time dropped "Moonlight Shortsword (War, Rng, Brd, Rog) 1hs, Fear Washed Boots, Lesser Dreadmote, Bloodforged Chain Leg Ornament, Echo Of Shade."
Popped on bottom of stairs too. Dropped "Earring of the Crescent (no slot 3), Glowing Dreadmote, Bloodforged Plate Legs Ornament."
From what I see this mob DOES spawn from ANY "a wandering soul" around stairwell from top to bottom.