well i killed Xydusa and apparently he turned two of my members to stone??!!. what to do now, do i have a way out?? or shld i kikk her again from start??.
also tell me where to go after killing her

what you need to do is do the elevator maze. There's a bunch of elevators and stuff you need to take (I think a walkthrough of it is in the best tips thread, I'm not sure) and then you'll eventually find your way out. To bring your characters back from stone, you need to use the vine spell 'stone to flesh' (level 4 or 5 spell IIRC) or you can visit a temple to revive them.

You'll be right with the stoning most likely :D Yes, Xydusa can stone you among others.

If you don't want to get stoned then use the Merlin's Shield spell. You can buy scrolls with Merlin's Shield spell in the Mages Guild. The spell will boost your magic resistance to almost immunity so that all magical attacks against you will be ridiculous. Use the spell against dangerous spellcasters like Xydusa, salads and some others.

IIRC, the Stone to Flesh spell is a level 6 Stone spell. You can also find Stone to Flesh potions (orange). The Merlin's Shield is a level 5 Stone spell.