Protect Yourself From Magic
I found killing the lich in the Bridge District very easy after using a Protection from Magic scroll. I loaded by main character (Fighter/mage), used the scroll, walk in and patiently waited until the Lich's Improved Mantle wore off. The lich casted spell after spell but I was immune. In fact he gated in a Pit Fiend and I got to watch a great fight between them. I just kept swinging every round. Everything the Lich gated in, I back off and let the gated creature attack the Lich.

Submitted By: Jason

Daystar is the Key
Particularly, the Lich at the Inn in the City Gates section. Send in a hasted character, or a monk, and search the loot in the back of his room. Grab the Daystar longsword and run back out. He actually followed me, but my Paladin was able to cut him to pieces using the Daystar. A very tough battle was made much easier by the use of this sword.

Submitted By: DJ Swinger

Set Some Traps
I killed the lich in the bridge district and in the Cult of the Unseen Eye by setting traps where the lich appears after that you touch the sarcophagus. The lich appears and gets himself killed: traps are faster than any spell :-)

Submitted By: Raven

Line o' Sight
Go with a character wearing Boots of Speed to open the sarcophagus and imediately go down the stairs. While doing this, keep the rest of your party on the opposite side of the room. When the lich appears, it will initiate dialogue with the character who releassed it and then it will attack. Unfortunately for you, the lich casts right away things like Improved Mantle, Protection form Magic Weapons, Protection form Magic Energy, Fire Shield, etc. Your best solution here is to run with your character and join the rest of your party out of the lich's line of sight. Wait there patiently for 2 to 3 minutes until the spells of the lich run off. Then come back with all your party and take the lich down with arrows and melee weapons. You will hit so often that it will be unable to cast spells and eventually will die.

Submitted By: Silviu

Spell Immunity/Conjuration and Mass Invisibility
Ok, I used spell immunity, abjuration and when a lich/mage cast time stop, nothing happened! I was not immune to it! So, i did this, liches like to cast symbols alot, these are very deadly because they have a good radius, good save penalties, and the Fear Symbol is the worst. So, instead of wasting the Spell Immunity, set it to Conjuration, this will protect your mages from Fear and Death Symbols so they can continue to pound the lich/mage. Also, Mass Invisibility kills in theory, nearly all mage/lich spells are cast on a person, so if they are unable to target you, they are way easier. This also helps during a Time Stop because you get bonuses to saves and they cannot target you with Symbols which they always target an actual person.

Submitted By: Visjerei

Enter and Exit
The lich in the City Gates district is very easy to take out. All you have to do is enter the room and when he begins to cast, get out of the room, then re-enter the room. The cast will be cancelled and he will start casting again. Do this several times and, at a certain point, he won't have any spells left, so you can just kill him.

Submitted By: Sir Dargor

Vhailor's Helm and Daystar
This is a simple strategy that I find works awesome against all liches and vampires.

1) Buy Vhailors Helm from the bonus merchant in the Ribalds store and equip it to your tank. If you do not have enough money go to the shadow thieves guild bottom floor and you can sell an expensive item and steal it back and sell it again as many times as you like.

2) Kill the lich in the Crooked Crane (the inn in the city gates) to get Daystar. Do do this have a thief run hasted and invisible up to the crate behind him, lockpick the trunk and take the sword. Then identify it and give it to a tank. Go to items and cast sunray (with any luck this will kill the Lich, if not go up to it and hack it to pieces with Daystar.)

Now you have the required eq for this strategy now it is simple you just:

1) Cast simulacrum with Vhailor's Helm before you face the lich

2) Have your tank and his double both cast sunray ASAP with any luck you will do 1064 damage twice but if not depending on how much hp the lich/vamp has it will already be killed. If it has alot of hp just try again and do massive damage with the sunray and hope he doesn't save vs spell.

Submitted By: Skynx

Polymorph Self!
Simply transform yourself into a mustard jelly. With 100% magic resistance he cannot harm you in any way except with normal and weak attacks. Walk up to him (alone, of course...) and wait until he has used all his spells and switches to a melee attack. This will take some time but then you can rush him with the rest of your party and simply finish him off. I killed him with my Cleric/Mage(lvl 9/11). No hard fight with this strat though it's advised to take some healing potions with you...

By the way, this tactic works against many spellcasters.

Submitted By: MrRieper