I don't believe it's possible to get a wraithwing to go over that bottom arrow.
If you had a rock golem that moved before the serpent, you might be able to lure it up after you to kill the serpent...but I'm betting that won't be possible either.
(I don't have my demos for this room, so I'm guessing).
It looks to me like you need to do this:
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Use the two WWs to kill the serpents in the top half of the room, then force one down past the left force arrow.
Then go down into the room with the other WW, release it, use it to kill the serpent in that room, then kill it.
Now you can cross over to the other room, kill all the golems and then push the WW up to kill the serpent.
I think that approach should work, although it's possible that I've missed something.
Josh
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"
Rings and knots of joy and grief, all interlaced and locking."
--William Buck
