AHH need Shadow Lich HELP!!

All is going well...im minding my own buisness going doing some quest to stop the cult of the lidless eye. So I figure geez they are blind how hard can it be. All of a sudden i open a coffin and out pops a Shadow Lich. I tried and tried and tried some more to drop the bastard but to no avail. This guy just wont die. I am a mage. I have Misnc, Korgan, Aerie, Jahiera and Yoshimo in my party.

I tried fireballing it, I tried breaching it, I tried hitting it and so help me i even tried going it around it but nothing. It seems i just gotta fight this thing and i dont know how. The most i ever got it to is barely injured and thats that. It just pulls the Death Spell on my sorry ass and im gone man. I tried Miscast Magic, I tried interupting its attacks. I tried every freaking thing and nothing works. All my spells just says "Shadow Lich: Spell Ineffective"

Help me out guys what can I do??

Ok there already are many tactics on this board but here is mine.
1. Make youre mage learn or have a scroll of lower resistence or the other magic resistence reducing spells.
2. Make Jaheria cast Insect Plague as quick as possible.
3. Make your mage cast Melfs Minute Meters again and again they are thery good agansit lichs.
4. Make Aerie cast spells like animate dead
5. Make Aerie use a very high quality sling.
6. Make yoshimo set traps
7. Make someone cast true sight when the Lich makes a copy of itself.
Those are my tactics

[el_kalkylus]

My tactic is:
If you have an assasin, cast invisibility on him or use potion. Then poison your blade and backstab the Lich. It usually dies immediately if all attack it with little spells and so forth. I once hit 96 damage on the lich with one blow, and I was at level 10. With your mage you will probably have to do it the hard way like above.

Oh yeah, you have to prepare yourself before the fight with haste and hopefully you manage to hit the lich before it starts talking and getting all the protection spells.

i cant find that lich, i have the golden torso, all i need are the legs and the arms,
does it matter if i slaughterd the kult without getting the key for the door,
i cant find the key on anybodys corpse