Grim Knight

Your time spent dealing out death on the battlefield has caused a powerful entity to gain interest in you. Some might call this being a specter, some a Lich, but those who are touched by this power know that it is Death itself that calls out to you. Falling somewhere between the extremes of good and evil, you have a unique understanding and appreciation of the forces of death, knowing that it exists as a balancing force in the universe not bound by the sway of one extreme or the other. You have been chosen to be Death's hand, the deliverance of its cosmic balance, but can your soul survive this task?

As one of Death's reapers, you gain the ability to command the powers of death to bring justice and a final end to your enemies. Sacrificing your own body in the process, you hand out the judgement of eternal balance in the hopes of keeping the scales where they must be.

Level 3: Unholy Bond

The connection you have gained with your chosen weapon to deliver death to your enemies allows you to form an unbreakable bond and increase your martial prowess.

Death Rite: You learn a ritual that creates an unholy bond between yourself and a two-handed weapon of your choice. You may perform the ritual any time you finish a long rest, and the weapon must be within your reach throughout as you use your unholy power to etch runes into it. Once you have bonded a weapon to yourself, you can’t be disarmed of that weapon unless you have the incapacitated condition. If your weapon is on the same plane of existence, you can summon that weapon as a Bonus Action, causing it to teleport instantly to your hand.

Death's Reach: While you are wielding your bound weapon, the spirits of the damned rise to aid you. If your bound weapon has the reach property, you receive a +1 bonus to your AC., if it does not have the reach property then you gain a +1 bonus to attacks made with the weapon.

Level 3: Reaper

Your experiences with war and combat have drawn forth from you a special connection with death. This connection strengthens some of your abilities while granting you access to runes of power that you can use to fuel your unholy abilities.

Death Runes: You gain 3 death runes, these runes are used to fuel your otherworldly powers or augment your attacks. You may only consume a number of runes each turn equal to your fighter level divided by 3 (round down), and all runes are returned upon completing a short or long rest. You gain an additional death rune for each level of fighter you gain. 

Unholy Powers: You learn 3 Unholy Powers of your choice from the Unholy Powers list, and you may use an Unholy Power only once per turn. You learn an additional Unholy Power of your choice at 7th level, 10th level, and 15th level. Each time you learn a new Unholy Power, you may also replace one you already know with a different one.

Saving Throws: If an Unholy Power requires a saving throw, the DC equals 8 plus your Strength modifier and Proficiency Bonus.

Chill of the Grave

When you hit a creature with a melee weapon attack, you may expend one Death Rune to add 1d8 cold damage to that attack and reduce the target's speed by 10 feet (minimum 0) until the start of your next turn.

Dark Command

As an action, you may expend one Death Rune and issue an unholy challenge that compels other creatures to do battle with you. Each creature of your choice within 15 feet of you must make a Wisdom saving throw. On a failed save, a creature has disadvantage on any attack roll that isn't made against you for 1 minute. An affected creature can repeat the saving throw at the end of each of its turns, a successful save ends the effect.

Death's Visage

As a bonus action, you may expend a Death Rune and summon an illusory image of Death in a space that you can see within 30 feet of you that lasts for 1 minute. This image is stationary and may not be moved, it is also insubstantial and may be passed through freely. Any creatures of your choice that are within 15 feet of the illusion when it is summoned, or that move within 15 feet of it while it is active, must make a Wisdom saving throw or gain the Frightened condition for the duration with the target of their fear being the illusion. Affected creatures may repeat this saving throw at the end of each of their turns, ending the condition on a success and becoming immune to this instance of Death's Visage.

Reap

When you hit a creature with a melee weapon attack, you may expend two Death Runes to add 1d10 necrotic damage to the attack. This damage is doubled if the target is bloodied.

If this attack is used as the triggering attack of your Sow ability, and lands a critical hit or reduces a creature to 0 hit points, then you regain the runes spent for this attack.

The damage dice of this attack becomes a d12 at level 15.

Shadow of Death

As a bonus action, you may expend one Death Rune to become wraith-like and ethereal. Until the end of your next turn your movement is unaffected by difficult terrain and you may pass through creatures or objects. You can also spend 10 feet of movement to automatically escape from non-magical restraints, such as manacles or a creature that has you grappled.

Silence of Death

When you hit a creature with a melee weapon attack, you may expend one Death Rune to attempt to silence the target. The target must make a Constitution saving throw, on a failed save the target becomes silenced (it may not speak or cast spells with verbal components) until the start of your next turn.

Soul Shield

As a reaction when you are hit by a melee attack, you may expend a Death Rune and gain a +5 bonus to your AC until the start of your next turn. If this bonus would cause the triggering attack to miss, you may immediately make an attack of opportunity against the triggering enemy. 

Sow

As a bonus action, you may expend one Death Rune to help improve your chances of landing a strike. Until the end of your next turn, you may choose one attack and gain advantage with that attack (you must declare you are using this advantage before rolling the attack). Additionally, when you make this attack you score a critical hit on a roll of 19 or 20 on the D20.

Vampiric Strike

When you hit a creature with a melee weapon attack, you may expend one Death Rune to add 1d8 necrotic damage to that attack. You regain hit points equal to the necrotic damage that you deal from this ability.

Vein Tap

As a bonus action you may expend one Death Rune and immediately roll available Hit Dice up to an amount equal to one quarter of your Fighter level (rounded up). You lose an amount of hit points equal to the total rolled, but gain twice that number of temporary hit points. You can not benefit from healing effects other than those provided by Vampiric Strike or Necrotic Carapace until the beginning of your next turn.

Level 7: Dying Grasp

Starting at 7th level, you can channel unholy power to pull a creature toward you and - ultimately - its grave. On your turn, you can use a Bonus action to reach out with an ethereal, undead arm to pull one enemy that you can see within 30 feet towards you in a straight line. The creature stops moving when it is within your current weapon's reach or if it collides with any other terrain or creature, whichever comes first. You may only grip a target up to one size larger than yourself. Once you use this feature, you must finish a short or long rest before you can use it again unless you expend two Death Runes to regain the use of it (no action required).

Level 10: Unholy Surge

Starting at 10th level, your Unholy Powers that deal damage increase by one die. In addition, whenever you roll initiative and do not have any remaining Death Runes you may regain up to half of your total death runes and expend 5 hit points for each rune gained in this way. Once you use this feature, you can not use it again until you have finished a long rest.

Level 15: Necrotic Carapace

Starting at 15th level, your communion with Death has had a great effect on your body. Your skin becomes pallid and your eyes adopt an eerie green glow, an unmistakable mark of your connection to the death you deal out. You become immune to necrotic damage and if you would take necrotic damage you instead regain hit points equal to half of the damage you would have taken. Additionally, you are now immune to attempts made by undead creatures to frighten you, and you ignore the negative effects of cold environments.

Level 18: Death Becomes You

At 18th level, your connection to death becomes so strong that you may temporarily invoke the spirit of Death itself. As a bonus action, you assume the form of a terrifying grim reaper for 1 minute, gaining the benefits below.

Flight: You sprout horrific black spectral wings from your back and gain a fly speed of 60 feet, and the ability to hover.

Commanding Aura: When you activate Death Becomes You, you may immediately use Dark Command as a free action without expending a Death Rune.

Unstoppable Terror: The bonus granted by your Unholy Bond increases by 1, all of your Unholy Powers that deal damage increase by one die, and for every enemy you critically hit or reduce to 0 hit points while in this form, you gain temporary hit points equal to half of your fighter level (round down) plus your Constitution modifier.