Finally, after days of checking back repeatedly, and then half a day of solid camping the entire room, Skullrend popped in the north-central part of the room, straight in front of the tunnel entrance. I'd managed to kill every other named in the zone between the locked door and Vergalid himself, spotted all of Velosk's spawn points including the one way down in the Pit of Doom. And this was on Thanksgiving when we had 50% increased rare spawns! Talk about an unnecessarily rare mob! I finished the entire Shield of the Otherworld achievement before I got this guy to show up once!
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Medya Wyvernslayer <Council of the Phoenix> Magician, Rizlona TLP
Once you are keyed for deeper Vergalid, travel through the door. At the bottom of the tunnel, is the first of two pool areas which have one roaming granite sentinel, three golems, and a couple of drakkin. The granite sentinels are PH for Vu'Ryn the Stone Guardian. Supposedly, the first golem in the pool you see when entering the area is a PH for Velosk, although I have never found him there. The other 2 golems in this same pool are PHs for Skullrend; 3 of my 6 spawns occurred at the middle golem and 1 of 6 spawns occurred at the other golem in the area which was marked on my map. At the second pool, the first golem spawned Velosk 8 times while I was farming Skullrend. The middle golem was a PH for Skullrend 2 of 6 spawns. This was my experience while farming Skullrend for my group.
He finally spawned at the pond near 312 ,-1913. Velosk also spawns in the same area.The pond is before the hall with the void-spawned and Green Legion Corpsetenders.
In the water area just beyond the door there are "clattering" skeleton golems and on the ramp there are 2 types of "void" skeleton golems - there guys are numerous and I suspect not the PH's.
Likewise there are 2 in the water area and I think 2 down the ramp that are "dark" something or rather golem skeletons that are much darker in colour and I suspect that these 3-4 skeletons are the PH's - on the ramp these are the locations where the named pop at least and I recall seeing Skullrend in one of my first times into the water area on the dark skeletons spot.
To camp one area or the other, probable easier to work the ramp for better XP - start at the top and clear to the bottom, invis up and run back up to top and repeat - did this easy 3boxing with mercs is a little costly as the plat from looting isn't much but the loots being sold just keeps you ahead cost wise.
Cleared the large spiral ramp 20-30 times in an agonizing camp, then went to bed and woke up to find him up... but in a different spot to what I'd been clearing. I found him at 255, -1900, -585 near Vu'Ren.
Like Velosk, I've seen him and spawned him in several different places...I'm thinking actually there's 4 or 5 different bone golems in zone that can PH for him, Velosk, or Rul Shadowfang, because I've seen each of them up at each of the places..
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Toucan Tanksem of Vallon Zek, Sebilis, Venril Sathir, Antonius Bayle, and now Toukan of Povar