[1.6.5] EoR Final boss can warp out of area

[Dracos]

About the only thing I can bug in a run of the final that's so frustrating on nightmare, I'm ready to fling my keyboard:

The sher'tul high priest can warp entirely out of the battle area. It does look like triggering the battle area limits will get him warped back, but he really shouldn't be using teleport type stuff at all and this at least can leave you with no boss in the area to fight at all. With so much space and summons, having the boss fleeing entirely can be deadly on its own fronts, as the 3(4-5 with clones of themselves) god parts can bury you under summons as you fruitlessly look about the space for a target that at least helps move the fight toward conclusion.

Whining:
In general, the fight could use more move toward conclusion (whether via ridiculous murderbeam to player or less ridiculous defenses). I've had a couple of runs where the fight goes for thousands of turns just becoming increasingly frustrating. This one has the brutal dark feed + teleport + time shield + massive summon piles (from the god parts) + Bone shield + Teleport + Blink + Spine of World + Near Immune Confusion/Stun. The eyes sleep/waking over and over again with +10000 point heals are almost unneeded against the sheer unendingness this produces of the vast majority of attacks just being noped and the boss being able to just warp away and come back with full bone shield and time shield. I get it, it's a dramatic finish fight...but basically the boss is rarely blasting me for dangerous (1600) damage amounts that are likely to kill me outright... and commonly just plinking me weakly even with all the status output it does while it stands there immune...before hopping away again.

I've no idea what I can practically do, besides quit the game or stand there and let him kill me, to wrap up the fight. Anhillator doesn't have sustain removal, and only down one tree has benefit removal, so I can't really go 'I should've been built differently for this fight'

[Beartrap86]

I feel the exact same way, I've lost 3 endgame characters to him and there's nothing I could do. 2 Sawbutchers and an Archmage. You have to burst him down or you just are screwed. EoR seems to be crapshoot as I breeze through the whole game and then have no way to ever get the priest down past 40%.

Help is appreciated on how to beat him? I never have.