Inspiration from SwordMeow's Atavist Class

Electric Viscera

Your blood courses with power. You learn the shocking grasp cantrip. It counts as a warlock spell for you.

Expanded Spell List

The Atavist 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.

Atavist Expanded Spells

Rend Ichor

At 1st level, you can tap into your raw health to deliver death. You have a rend die which is a d6. After you hit with a melee attack, you may roll this die and add the result to the attack's damage roll. Your maximum hit point total is reduced by the amount rolled.

After a long rest, your maximum hit points return to their original amount.

At 6th level in this class, your rend dice increases to 2d6. At 10th level in this class, your rend dice increases to 3d6.

Wounded Nature

Beginning at 6th level, you gain finer control over your ability to sacrifice life.

Select two of the following Wounded Nature abilities. You may change your selections after a long rest.

Alacrity

You hover in and out of a foe’s reach, stepping between it as easily as a flick of a blade. You can take the Disengage action as a bonus action.

Beating Reflexes

After you roll a Strength or Dexterity ability check, but before you know whether it succeeds or fails, you may roll your rend dice and add the result to the roll. Your maximum health decreases by the result.

Control

You finely manipulate your blood. When you rend ichor, you can reroll the rend dice once per turn and choose either result. 

Prime Condition

While above half your hit point maximum (rounded up), when you rend ichor the result is doubled.

T-Cell

As a bonus action, you mark a creature for execution. The creature remains marked for one hour or until you use this ability again. When a marked creature dies, you may roll your rend dice. Your current and maximum hit points increase by double the result. Once your hit points increase this way, you can’t use this feature again until you finish a long rest.

Thickening Humors

When you have taken damage and are below your hit point maximum, your blood pools heavy on your weapon. You add your Constitution modifier to your melee attack rolls.

Transfusion

You can sacrifice your health to heal others. As an action, you may roll your rend dice. A target creature within 5 feet regains hit points equal to the result. You lose hit points equal to the result. This loss cannot be reduced in any way.

Wounded Driven

When you have taken damage and are below your hit point maximum, your blood pools heavy on your weapon. You add your Constitution modifier to your melee attack damage.

Bloody Vengance

Starting at 10th level, your connection to your blood allows you to defy death. When you are reduced to 0 hit points, you can use your reaction to drop to 1 hit point instead and cause your body to erupt with blood. Each creature of your choice that is within 30 feet of you takes necrotic damage equal to 2d10 + your warlock level. You then gain 1 level of exhaustion. Once you use this reaction, you can’t do so again until you finish a long rest.

Master of Blood

Starting at 14th level, your hitpoint maximum resets when you take a short rest.