lichdom

You have undergone dark rituals to become a lich (keep in mind that the rituals to achieve lichdom are incredibly difficult to obtain such as making a deal with orcus) you gain the following benefits

Undead nature: you no longer need air,food or water and start to decay over the course of your immortality you also register as undead for all things

undead resistance: you become immune to necrotic damage and bludgeoning, piercing and slashing damage from non-magical attacks

Phylactery: you have crafted a powerful magical item that works like a soul tupperware that you need to feed a new soul every month. when you die you reform in 1d10 days within 5 feet of it.