I'm planning on roleplaying a mage who will, as the Oblivion crisis rears it head, decide that the only way to defeat it (since it all seems to be on his shoulders) is to become a Lich. The immortality (of a sort) and extra power will be useful considering I will be also using a M.O.E moduel that undermines the levelled gamepaly. So my lowbie-mid-level Mage will be running into things dozens of levels tougher than himself.
Problem is... i'm having problems deciding when that point will occur. I'll me using the Mages Guild quests to reach the prerequisite level 23; with the spell-making alters of the AU that shouldn't be a problem. What is an issue is that I can't think of a single point in the main quest that seemed intimidating enough (or borderline impossible) that would drive a Mage to give up their humanity because "it's the only way". I want to make a noble Lich; there have been a few examples in ES lore of people who have done so for a good cause. i can't think of a better cause than closing shut the jaws of Oblivion. Except... if my character can survive the quests at all with undermined leveled lists then I can't think of a single part of the quest that would make a Mage think "No, i can't do this... but... wait."
Advice?