Soul Warrior

A death knight was a mighty undead warrior created by gods of death or other malevolent forces. They were most commonly created from evil humanoids who in life had been blackguards, fighters, rangers, barbarians, and even paladins fallen from grace.

Regardless of their past lives, all deathknights shared something in common, a robust unkillable nature. This endless life without rest had 2 spheres of thought connected to them. The first was adopted by those who still served the dark gods they did in life, that this second unlife was a blessing and a chance to serve their dark god better than they ever had in life. The second sphere was more somber. These deathknights viewed their unlife as a punishment for the vile crimes they had committed in life, and many who rose once more with this guilty conscience did so with the perception of self retribution. Deathknights who held these beliefs often stride through the world with the sole desire to help those around them, in order to redeem their past lives and help far more than they ever harmed.

Spellcasting

When you reach 3rd level, you augment your martial prowess with the ability to cast spells. See Spells Rules for the general rules of spellcasting and the Spells Listing for the warlock spell list.

Cantrips

You learn two cantrips of your choice from the warlock spell list. You learn an additional warlock cantrip of your choice at 10th level.

Spell Slots

The Deathknight Spellcasting table shows how many spell slots you have to cast your warlock spells of 1st level and higher. To cast one of these spells, you must expend a slot of the spell’s level or higher. You regain all expended spell slots when you finish a long rest.

For example, if you know the 1st-level spell arms of hadar and have a 1st-level and a 2nd-level spell slot available, you can cast arms of hadar using either slot.

Spells Known of 1st-Level and Higher

You know three 1st-level warlock spells of your choice.

The Spells Known column of the Deathknight Spellcasting table shows when you learn more warlock spells of 1st level or higher. Each of these spells must be of a level for which you have spell slots. For instance, when you reach 7th level in this class, you can learn one new spell of 1st or 2nd level.

Whenever you gain a level in this class, you can replace one of the warlock spells you know with another spell of your choice from the warlock spell list. The new spell must be of a level for which you have spell slots.

Spellcasting Ability

Charisma is your spellcasting ability for your wizard spells, since your spells are generated through your undead connection. You use your charisma whenever a spell refers to your spellcasting ability. In addition, you use your charisma modifier when setting the saving throw DC for a warlock spell you cast and when making an attack roll with one.

Spell save DC = 8 + your proficiency bonus + your charisma modifier

Spell attack modifier = your proficiency bonus + your charisma modifier

Deathknight Spellcasting

Fighter Level	Cantrips Known	Spells Known	— Spell Slots per Spell Level —
			1st	2nd	3rd	4th
3rd	2	3	2	—	—	—
4th	2	4	3	—	—	—
5th	2	4	3	—	—	—
6th	2	4	3	—	—	—
7th	2	5	4	2	—	—
8th	2	6	4	2	—	—
9th	2	6	4	2	—	—
10th	3	7	4	3	—	—
11th	3	8	4	3	—	—
12th	3	8	4	3	—	—
13th	3	9	4	3	2	—
14th	3	10	4	3	2	—
15th	3	10	4	3	2	—
16th	3	11	4	3	3	—
17th	3	11	4	3	3	—
18th	3	11	4	3	3	—
19th	3	12	4	3	3	1
20th	3	13	4	3	3	1

Soul Weapon

At 3rd level, you learn a ritual that creates a magical bond between yourself and one weapon, binding your soul to it in a similar fashion a lich does a phylactery. You perform the ritual over the course of 24 hours. The weapon must be within your reach throughout the ritual, at the conclusion of which you touch the weapon and bind your soul within.

Once you have bonded a weapon to yourself, you can’t be disarmed of that weapon unless you are incapacitated. If it is on the same plane of existence, you can summon that weapon as a bonus action on your turn, causing it to teleport instantly to your hand.

You can only bond with 1 weapon at a time. 

You soul weapon stores your soul when you die, negating the material costs for spells like revivify when used to bring you back to life.

Your soul weapon has a damage threshold equal to your level, an ac equal to 10+ your proficiency bonus, and a number of hit points equal to twice your level.

Undead Horseman

Beginning at 7th level, You learn the find steed spell and can cast it once per day without spending a spell slot. Additionally, once per day when you cast find steed, you can instead summon a Nightmare. This nightmare follows your commands and acts on your turn.

Once you've summoned a nightmare in this way, you cannot do so again until you've completed a long rest.

Soul strike

At 10th level, you can channel the negative energy in your soul into your weapon strikes. When you hit a creature with your soul weapon, it takes additional necrotic damage equal to your charisma modifier.

Soul Siphon

At 15th level, you gain the ability to feed on the dying energy of those around you. When a creature dies or is dying within 30 feet of you, you can use your reaction to siphon what remains of its fleeting life into yourself. You regain a spell slot of a level equal to half of that creature's CR, or you can gain temporary hit points equal to the creature's CR.

You can use this feature a number of times equal to your proficiency bonus.

Undead Warlord

Upon reaching 18th level, you have become a paragon of undeath. Undead with a cr of up to 1/3 your level or lower no longer attack you and you can attempt to take control of those very same undead. When you do so, the target must make a wisdom saving throw or become dominated as if effected by the dominate monster spell. You can dominate a number of undead with a total cr equal to 2/3rds your level. 

Additionally you can no longer be killed while your weapon is intact, however if you have taken damage equal to twice your hp, and your weapon is destroyed, you immediately die.