@Goldfish
Blindsight will do nothing against Darkstalker.
Dimensional Anchor could work if you can pinpoint the square, it would just have a miss chance, not great but it's not uncastable as some were saying.
Not quite true. Viserys will be required to make a Listen check with a +15 bonus against the Dogoi's +26 Move Silently bonus. Not exactly good odds, but not insurmountable. Luck can be on our side for once.
I'd rather Dimensional Anchor him.
If he can't teleport, he is fucked. He can't fly, Fog Cloud won't save him from Blindsense from Viserys, much less Oathkeeper.
Plan updated with insights from TNE and Deliste.
[X] Viserys casts Nerveskitter on Tyene.
-[X] Tyene casts Close Wounds on the Renplacement, then casts Blindsight on Viserys.
--[X] If Tyene casts Blindsight on Viserys before his turn in the Initiative order comes up, and he is able to pinpoint the Devil's location, he targets it with Baleful Polymorph, transforming it into a turtle. If it resists, he casts Celerity and targets it with a Dimensional Anchor spell. If it fails to resist, Viserys uses Greater Shadow Enchantment as detailed below.
--[X] If Viserys comes before Tyene in the Initiative order despite the Nerveskitter effect, or he fails to locate the Devil sufficiently to target it, he uses Greater Shadow Enchantment to duplicate a Greater Command spell, ordering
everyone except for Richard, Garin, and Tyene to Halt.
-[X] If Viserys turtles the Devil, Richard moves to subdue Criston non-lethally, though maiming is not frowned upon. If Viserys instead Halts everyone, Richard activates his Earring's See Invisibility power and moves to carve the Devil into sushi.
-[X] Garin continues trying to murder the Devil, unless Viserys successfully turtles it.