Curse - Full Skeletal Curse

Through one way or another you have taken on a more skeletal guise. Most commonly, this state is contracted by a powerful curse, but failed animated dead or resurrection spells can cause the same result.

Some skeletons after being left alone for awhile will resort back to habitual behaviour they've exhibited in life, such as a former miner mining ore, or a guarding taking up post. 

Undead Nature. You don't require air, food, drink, or sleep.

Skeletal Body. Your newfound undeath rewards you with a few perks, but your body is not as stable as it used to be. You gain vulnerability to bludgeoning damage, immunity to poison damage and are immune to the poisoned condition as well as Exhaustion.

Visage of the Reaper. Your face and body giveaway your undead nature. Most humanoid cultures will be scared of you if they become aware of what you are, unless you disguise yourself. The extent of this is up to the DM. 

End of the Line. Unless the curse is broken, you can only be raised into your undead body, forcing your soul back into this skeletal form.

Ancient Curse. On this curse, the spell remove curse simply fails, as means short of a wish spell or other legendary means cannot break it.