I haven't even tried going after the Daystar and such yet, so haven't gone up against the lich, but if you're playing a char with enough thief-class in him to set traps, setting a lot of those and making the badguy chase you REALLY helps most of the time. And if you're invisible, they generally chase you, but miss you with spells and effects, at least until they cast true sight.
Also, if the lich himself isn't in one of those rooms where the whole party has to enter together, summoning a lot of creatures and then sending them into the room with it without your PC can help too, makes the bad guy use up some of those spells and abilities, even if he does take 'em out fast. And I *think* you can use protection spells on summoned creatures that'd stop them from being confused or dominated if you have those spells...I know haste and protect evil 10' radius will cover them if they're close when you cast.
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Playing the cutest li'l Chaotic characters since 1996.