[AlexanderHowl]

Using the phylactory as a magical gadget is a valid way of having a Lich. In that case, I would modify the positive traits of the above 300 CP version with Amulet, Protected, -35% and Magical, -10% and give the disadvantage Mitigator, Constant, Rare, -50%, for a value of ~175 CP. In that case, the advantages and disadvantages of being a Lich only exist while wearing the phylactory.

A more nefarious version would have the phylactory inflict Dependency (Constant, Phylactory) [-150 CP] and Fragile (Unnaatural; Mitigator, Phylactory, Constant, Rare) [-25 CP] to a character when they attune to the phylactory, making the package into a 0 CP feature. Attunement would only require a character to wear the phylactory for a minute. If the phylactory is stolen or destroyed, they have (HP×2) minutes before they expire. That type of item would likely only be suitable as a cursed item though.