She walked to me with a scythe that was spitting out smoke as black as shadow, she never stopped to look at the corpses of my family she  had slaughtered. My son who had trained to be a knight, had been slain instantly by her scythe. My beautiful daughter, whose beauty had entranced all the men in the nation, whose headless body was laying on the floor. My Wife, whom stood by my side when I killed those heretic that dare spit in our gods face, was now split in two at the waist. "Why?"  I asked the monster who did this: "WHY DID YOU KILL MY FAMILY!?"
The woman stopped and answered me for the first time; "Why, you ask my lord? Because you killed mine of course. Do you not recognize me?" She pulled down her hood, and I remembered her well, she was the child to some of the heretics I had tortured and killed in my dungeon, a girl who had escaped from the dungeon 10 years ago. She pulled up her sleeve to show me her arm and I was terrified. It was translucent blue and you could see her bones clearly in this translucent arm. She then swung her shadowed scythe to my chest, upon it disappeared in a black smoke. leaving a hole in my chest. She knelled before me and smiled, saying "Death is equal my lord, and it comes for all". Then she put the bony hand of hers on my forehead, and everything turned black. 
                                                                                   
                                                                                  -Lord Federo Harawo Kallstrin, his last moments written down in the book of the dead in the Raven Queens palace

 

 Grim Reaper

Your patron is a being than can only be called Death, neither form, name or motivation drives Death, it is no god, yet god fears it. Pact with this being is neither good or bad, as death happens either way, it is one of the universals laws of the multiverse,. You can be a Grim Reaper who fights for justice, or just for personal greed, it matters not in the way of death, because death is equal to everyone. Your patron is rare, in that they will only notice you in places of large amounts of death, places like massive graveyards (during mass funerals), battlefields or places where people are killed en masse (like a prison that execute prisoners in the thousands or similar). 

Your patron will never smile or anger towards you, nor manipulate you, Death can only be pleased when death is caused, no matter how big or small. Death does not care what you do, and it does not care about the undead (as they died once during their turning). Death only wants you to at least kill something within a year, be it a bug or a tree, it does not matter, if it has a soul and can die is all that matters.

Warriors Of Death

The Grim Reapers are warriors of death, they are the rare who got the attention of Death and have chosen to spread the universal law of death upon those they want. You gain powers of a necrotic and illusion magical nature. When they make the pact with Death a chosen part of their body becomes translucent blue (it must be either an arm, leg, head or a torso), with only their bones being unaffected by this, this part of your body is what Grim Reapers use to send people to the afterlife(this does not make you undead, the body part is still there with the same needs as a normal living body). Many Grim Reapers and other kinds of Warlocks have debated over why just only the bone is the one of the chosen part of ones body that does not become translucent, and the most agreeable theory is that it is to symbolize that all creatures are white at the bone. Grim Reapers use a shadow-like scythe to deal with their enemies and many prefer the color black and hooded cloaks to wear. Some think that it was a Grim Reaper with a translucent skull that gave people the impression that Death was a hooded skeleton with a scythe. Many Grim Reapers tend to go on a quest for revenge when they make their pact, and are mostly of a chaotic alignment and often fight in the dark, being silent as Death itself.

Expanded Spell List

The Grim Reaper pact 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.

Grim Reaper Expanded Spells

Armored Reaper

At 1st level, you acquire the knowledge necessary to effectively protect yourself in battle, something you need if you are to get close enough to send someone to the afterlife. You gain proficiency with medium armor.

Shadow Scythe

At 1st level, you gain the ability to summon forth a shadow scythe without using an action.
It counts as a magical martial melee weapon with which you are proficient. It has the two-handed, reach and light weapon properties. It deals 2d6 + Charisma (minimum of 1) modifier in psychic damage, the moment this scythe leaves your hand it turns into black smoke and reappears in your hand when summoned again. You can dismiss the weapon at will without using an action, The Scythe can count as your Spell casting Focus.

Infused Death

At 6th level, you can feel the power of death run in your veins, giving your body resistance to Necrotic and Poison damage.

Extra attack

At 6th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.

Mass Death

Starting at 10th level, your attacks with your Shadow Scythe sweep through enemies near your target. Any Enemy within 5ft of the target takes half the damage you did to the main target.

Deaths Dance
Optionally you can choose not to make any extra attacks but spin around your own axis, sweeping trough any enemy within 10ft around you.

Avatar Of Death

At 14th level, you are a being which is a conduit for death to send souls to the afterlife. You are immune to Necrotic and Poison damage, and as a bonus action you can activate your Avatar Of Death state, which gives you resistance to slashing, bludgeoning and piercing damage for 1 minute. After which, you need a short rest to reset again.