undying rework based on lostfaith's

### The Undying
Death holds no sway over your patron, who has unlocked the secrets of everlasting life, although such a prize – like all power – comes at a price. Once mortal, the Undying has seen mortal lifetimes pass like the seasons, like the flicker of endless days and nights. It has the secrets of the ages to share, secrets of life and death. Beings of this sort include Vecna, Lord of the Hand and the Eye; the dread Iuz; the lich-queen Vol; the Undying Court of Aerenal; Vlaakith, lich-queen of the githyanki; and the deathless wizard Fistandantalus.

In the Realms, Undying patrons include Larloch the Shadow King, legendary master of Warlock's Crypt, and Gilgeam, the God-King of Unther.
#### Expanded Spell List
The Undying lets you choose from an expanded list of spells when you learn a warlock spell. The following spells are added to the warlock spell list for you.

1st *inflict wounds, ray of sickness*
2nd *blindness/deafness, silence*
3rd *revivify, speak with dead*
4th *aura of life, death ward*
5th *contagion, legend lore*

#### Defy Death
Starting at 1st level, you learn the *spare the dying* cantrip, which counts as a warlock cantrip for you. You are also immune to disease.

Additionally, you can use your magic to cheat the forces of death. Whenever you take damage, you can use your reaction to reduce that damage by an amount equal to your warlock level + your Charisma modifier (to a minimum of 0 damage).

You can use this feature once, and can do so again after a short or long rest. You can use this feature an additional time between rests at 6th (2 times), and 14th (3 times) levels.

#### Among the Dead
Starting at 6th level, undead have difficulty harming you. If an undead targets you directly with an attack or a harmful spell, that creature must make a Wisdom saving throw (an undead needn't make the save when it includes you in an area of effect, such as the explosion of fireball). On a failed save, the creature must choose a new target or forfeit targeting someone instead of you, potentially wasting the attack or spell. On a successful save, the creature is immune to this effect for 24 hours.

#### Undying Nature
Beginning at 10th level, you are immune to poison, can hold your breath indefinitely, and you don't require food, water, or sleep, although you still require rest to reduce exhaustion and still benefit from finishing short and long rests.

In addition, you age at a slower rate; for every 10 years that pass, your body ages only 1 year, and you are immune to being magically aged.

#### Eternal Life
At 14th level, your body is endlessly repairing itself. At the start of each of your turns, you regain hit points equal to your Constitution modifier (a minimum of 1) if you have no more than half of your hit points left. You don't gain this benefit if you have 0 hit points.

Also, if you hold a severed body part back in place over the course of a short or long rest, the part reattaches.