Base Class: Warlock
Your patron is an entity beyond time and history.
Expanded Spell List
The Eternal lets you choose from an expanded list of spells when you learn a warlock spell.
Replenishing Spell Casting
Starting at 1st level, your patron bestows upon you the ability to transmute the energy of your spells to bolster you. When you cast a Warlock spell of first level or higher, you gain temporary hit points equal to 1d6 + your level in this class. If this spell reduces a creature to 0 hit points, you also regain hit points equal to 1d6 + your level in this class.
Consuming Strikes
Also beginning at 1st level, your weapon attacks become more effective at draining your enemies. When you hit with a weapon attack on your turn, you can deal additional necrotic damage equal to 1d10 + your level in this class. This damage cannot be reduced in any way. You can use this ability twice before finishing a short or long rest.
Enervating Recovery
Starting at 6th level, healing you receive can be turned against your enemies. When you regain hit points from any source, you can choose an enemy target within 15 feet of you. That target takes necrotic damage equal to half of the hit points you regained as a lance of necrotic energy is thrust from within you. You can use this feature a number of times equal to twice your Charisma modifier (minimum of 1) before finishing a long rest.
Ceaseless Rejuvenation
Starting at 10th level, your vitality becomes easier to maintain and utilize. You regain hit points equal to 1d8 + your Constitution modifier (minimum of 1) when you are stabilized while dying. Additionally, when you are the target of a spell with the sole purpose of restoring you to life (but not undeath), you regain up to half of your maximum hit points.
Enduring Martyr
Starting at 14th level, you can use your depleted life essence to revitalize your allies and punish your enemies. When you are killed, your hit points are converted into a pool of healing and necrotic energy. You restore a number of hit points equal to half of your maximum hit points, divided as you choose among any number of allied creatures that you can see within 60 feet of you. Additionally, you can deal necrotic damage equal to half of your maximum hit points, divided as you choose among any number of enemy creatures that you can see within 60 feet of you. You can use this feature once every 7 days.