Questions
Is there a book covering the history of how Liches came to be? How about theories put up by players?
Do Liches automatically go insane over time?
Do they always turn skeletal?

Is there a book covering the history of the phylactery?
Was it given by a god/dess to a mage?
Did someone discover how to make one on their own?
Was it originally meant to the used the way it was? (Soul removed from contact with body and hidden elsewhere.)

Reason
What I'm wondering is if the phylactery was originally a public device which was inserted into civilians so they'd be revived in case of a tragic accident and someone else discovered it could do more, or that someone found a fully functional Auto-Revive System and tinkered with it to get what now causes a Lich.

Likely Answer
Yes, Liches were probably created by a mage in their laboratory for the express purpose of undead immortality or handed to someone by a god/dess, but does anyone know for sure?