Skeletions are immune to their attacks. Summon waves of them, eventually they thin down the hurd. It takes a very long time. There are also ways to make yourself tempoarly immune to their attacks. Phycialy they suck in a fight, long as your immune to them. Watch out for their Umber Hulk buddies though. Make sure your protected from their spells too.
My soulition in the underdark was my fighter/mage, with a cloak of reflection, immunity to charm magic, stoneskin, hasted, using brine potions, with tenser's transformation on him. Then run in the room with your 5 undead buddies and commence ta killen anything that moves. Leave your party way way way far behind. After about 30 seconds or so the flyers seem to run out of psionic juice and you can bring the rest of the party up for mopping.
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--Kellin da Mage--
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