One thing you could try is the need or power to feed on souls (without them going into a gem) Reasons could be: -Souls regenerate magicka, health and stamina -They can be used for some attack -Satisfy some need -Increase some kind of level etc Lore: Maylen Varen used souls to hold his soul in the star of azura how it was put was he would feed on the souls to keep himself from fading away, maybe you could use souls to keep your soul inside your phylactory. It doesn't break your theme of lichs working for all classes and in future it could be some way of getting to the ancient lich.