1: Perform a suicidal search for immortality, and die in the process, bribe dm with pizza to become one of those deathless undying ghosts from book of exalted deeds. Doesn't say it has to be good aligned. Your goal? Immortality/lichdom/whatever. Your now a ghost necromancer who does not need undead and are unaffected by positive energy a cleric channels.

2: Use spells like mage armor, shield (especially to block magic missiles being incorporeal), blur/concealment, ghoul touch, and spam your ghostly drain touchs at poor fools with non-magic weapons who can not harm you or even hit you at all and drain there wisdom/strength/etc and deal cold damage. Possibly taking levels in dread necromancer will up your melee touch attack power and slowly turn you into a lich WHILE BEING A GHOST.

3: Become a untouchable, invisible, incorporeal deathless lich, by this time, you have "survived" long enough to raise an army of spectral undead to go under your command and even take Undead Leadership with your insane charisma modifier to gain sentient undead as allies not directly under your control. Oh, obviously, con is a dump stat for this character, feel free to make it a 3...

Only 1 problem with this build. The prc you take to become the deathless ghost from the book of exalted deeds requires you to take it from 1 to 10 without break, and at 10, you fade from the world as your time is up. If this does not suit you, look up "The Ghost Ring", which is a magical item that makes the wearer a ghost, 100% garenteed, with there sanity/etc intact upon death. This way costs money, and youl be vulnerable to channel energy/etc, but still works out.