The Undeath

This Subclass focuses on the destructive powers of necromancy, and utilises various enchantment and illusion magics to compliment the fear-mongering abilities of it.

Spirit of Death

You can feel the forces of life and death wax and wane within others. As a reaction, you can return an incapacitated ally or yourself to 1hp a number of times equal to your proficiency bonus, with the charges returning at the next dawn.

Arise

You can recall the fallen, and control their corpses as you see fit. If you stand over a corpse for 10 minutes, you can add it to your Risen, a group of mindless soldiers who follow your will. The Risen retain their stat-blocks from life, with slight adjustments, such as every Risen gains immunity to necrotic damage, but vulnerability to radiant. Furthermore, any divine magic or traits the Risen had during their life no longer works, as their souls are no longer within the grasp of the Divine realm. 

You gain a number of Risen equal to your proficiency bonus + your spellcasting modifier, and these risen cannot have a CR higher than half your level, rounded up. 

When you Arise a fallen, you pick which form they take, with them becoming a skeletal, spectral or rotten warrior.

Rotten Form

Your Risen adopt a Rotten appearance, with their flesh and bone falling off of them. Rotten Soldiers gain resistance to non-magical slashing damage, but vulnerability to piercing. Furthermore, whenever they attack with a physical attack, the enemy must make a DC 12 constitution save or be diseased.

Skeletal Form

Your Risen adopt a skeletal appearance, with their flesh and sinew disintegrating off them. Skeletal Soldiers gain resistance to non-magical piercing damage, but vulnerability to bludgeoning. They also gain an AC of 15 (unless the stat-blocks is higher) and have an additional +1 bonus to attack.

Spectral Form

Your Risen adopt a spectral appearance, with their souls leaving their mortal shell behind. Spectral Soldiers gain resistance to non-magical bludgeoning damage, but vulnerability to slashing. Their non-magical attacks are also always counted as psychic damage, ignoring the damage type on the stat-block.

Bonesmith

During a short rest, you can create 1 item or piece of equipment out of bone and leather. Any item made must be non-magical, any armor or shield has a +1 to AC, and any weapon is considered magical and has a +1 to attack rolls.

To create the item or piece of equipment, you need twice the amount of bone in weight than the item requires, however the item does maintain its usual weight.

All objects created by this are obviously made of the corpses of others, and people wearing/holding these items have an additional +2 to intimidation whilst doing so.

Life and Deathless

You have fully grasped the line between life and death and move it at your will. As an Action you can enter a State of Deathlessness for 1 min, wherein any spells that do necrotic damage have the damage output doubled, and any necrotic damage you take is converted to healing. Furthermore, once per state of Deathlessness, you return to half health upon reaching 0 hit points.

However, if you are incapacitated a second time during the same State, any death saves are made with disadvantage.

You can enter this state a number of times equal to your proficiency bonus per week

Expanded Spell List

At 1st level, the Undeath 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 level: Inflict Wounds, Ray of Sickness

2nd level: Gentle Repose, Wither and Bloom

3rd level: Animate Dead, Speak with Dead

4th level: Greater Invisibility, Phantasmal Killer

5th level: Raise Dead, Contagion