The Soul Collector

Your patron is a collector of souls, whether for power, use as currency in the Nine Hells, to look at like imprisoned butterflies, or some other reason known only to them. This being's ultierior motive might be unknown to you and so too might the reason it has agreed to serve as your patron be inscrutable, but what it wants you to do is very obvious. It has a hold on your soul in exchange for giving you power and it wants you to collect more souls for it. Collectors of souls might be a lesser devil, a lich seeking to sustain itself by feeding souls to its phylactory, or some other entity.

Expanded Spell List

1st - Bane, Dissonant Whispers

2nd - Aid, Spiritual Weapon

3rd - Animate Dead, Revivify

4th - Death Ward, Ice Storm

5th - Antilife Shell, Banishing Smite

Soul Debt

Starting at level 1, your patron has a hold on your soul, weakening your body. Your movement speed is reduced by 5ft, and your maximum health is reduced by your proficiency bonus. However, when you kill something with a soul or something with a soul dies within 10 ft of you, you automatically collect their soul, temporarily giving you power. You gain 5 movement speed per soul thus collected and your maximum health increases by your proficiency bonus. You also heal 1 health every time you collect a soul, unless you are at maximum health, in which case your health now matches your new maximum. You can collect a number of souls equal to your proficiency bonus. Half of your collected souls disappear at the end of a short rest and all of them disappear at the end of a long rest or if you drop to 0 health.

Deathly Charge

At 6th level and onwards, once per short rest you can use your action to do a Deathly Charge. You are pushed forward for double your movement speed while ignoring difficult terrain and at the end of the Deathly Charge, can make a weapon attack or cast a cantrip spell attack, but the attack must be capable of only targeting one creature. The attack deals an extra 1d8 necrotic damage on a successful hit.

Shieleded Soul

When you reach 10th level, your soul has become precious to your patron. You gain resistance to necrotic damage.

Crystallized Souls

When you reach 10th level, you are able to dispense and detonate souls at your patrons will. You can release a soul to create a Soul Crystal, being able to create one from touch or 30ft. This is to be performed as a bonus action or reaction. When they detonate, they detonate in a square and deal 1d8 force damage in its square, they deal 1d6 force damage in the square directly next to it. You can only have up to 8 Crystallized Souls at a time.

Soul Assumption

Upon reaching 14th level, you've learned how to use your collected souls as a weapon. As an action, you target a creature with a soul that you can see and release your souls. The target takes 2d10 necrotic damage per soul. You lose your souls when you do this. If the target dies to this attack, however, then you collect its soul.

Guided Charge

At 14th level, when you make use of your Deathly Charge, you can control the path you take instead of being pushed in only one direction. However, your movement speed is not doubled for the charge.