Undead Form

Your Intelligence score increases by 4 and your Wisdom score increases by 2. An ability score cannot be increased above 22 this way.
You become an Undead in addition to any other creature types you are. Spells, abilities and other effects, that specifically targets Humanoids or Undead of a certain CR, have no effect on you.

If a spell or ability other than your own would cause you to gain Hit Points, you gain that many temporary Hit Points instead. Healing Potions work on you as normal.

If an attack or spell would reduce you to 0 hit points, you can roll a Constitution saving throw with a DC of 10 or half the damage taken, whichever is higher, dropping to 1 hit point instead on a success. You can't use this feature if you take radiant damage or damage from a critical hit.

You stop aging, are immune to any effect that would age you, and you cannot die from old age. You don't require air, food, drink or sleep and magic can't put you to sleep against your will.
You may choose to stay awake during a long rest, spending at least 6 hours in an idle state instead. You can hear, see, and feel as normal in this state.