Apollyon

Gifted by the Raven Queen the ability to kill and devour the living and non-living things to send them to the Raven Queen's realm to be dealt with as well as energy to be used to fuel Apollyon. It appears as a normal human left arm that is bandaged from finger tips to shoulder. When the Apollyon is released then the arm transforms into a large black and red (shadowy ember) demonic claw. It is elongated in comparison to a normal human arm giving it reach.

When Apollyon is out, it can be used as a +3 weapon and shield.

Magic Weapons. Apollyon weapon attacks are magical.

Life/Undead Eater. A creature dies if reduced to 0 hit points by Apollyon and can’t be revived except by a wish spell. At that point the life and soul is devoured by Apollyon and sent to the realm of the Raven Queen. When a undead creature dies when its reduce to 0 hit points by Apollyon the energy that kept the creature undead (curses, summoner, etc.) is broken and the energy is consume to feed Apollyon and what little is left of the soul is sent to the realm of the Raven Queen. With undead, the wielder can take a bonus or reaction action to consume the energy that is released this allows the wielder to regain 2d6 HP. 

Celestial/Fiend Eater. When a Celestial/Fiend dies when its reduce to 0 hit points by Apollyon the wielder can take a bonus or reaction action to consume the energy that is released. This stops the Celestial/Fiend returning to the afterlife and Apollyon consumes this energy gaining 2d8 temp HP; this causes the spirit of the Celestial/Fiend to live within Apollyon until it is fully consume; this can take up to a few hours to days depending on how powerful the Celestial/Fiend was. The temp HP goes away at the end of the wielder's next turn.

Per DM's degression, the wielder of Apollyon needs to make DC Wisdoms saves during this time if the Celestial/Fiend was powerful enough to influence the wielder; on a failed save the influence because too much for the wielder and becomes more aligned with the Celestial/Fiend's alignment.
This does not mean that the Celestial/Fiend takes over the wielder of Apollyon. This Wisdom save can be repeated every hour until a success to made.

Disrupt Concentration (Costs 1 Charges). Apollyon targets a creature within 30 feet of it who is concentrating on a spell. The target must succeed on a DC 16 Constitution saving throw or its concentration is broken on the spell.

Consume Magic (Costs 2 Charges). Apollyon can use a reaction to absorb a spell that is targeting only the wielder of Apollyon and not with an area of effect. The absorbed spell's effect is canceled, and the spell's energy—not the spell itself—is stored in the Apollyon. The energy has the same level as the spell when it was cast. Apollyon can absorb and store up to 5 levels. Apollyon can cast spells using spell levels stored in this way, and and the wielder of Apollyon gains 5 temporary hit points per level of that spell. The stored energy goes away after an hour if not used.

End Magic (Costs 3+ Charges). Apollyon can casts dispel magic on touch. This can be upcasted per charges.

Mother's Fate (Costs 3 Charges). Apollyon magical tries to engulf one creature it can touch. Make a melee spell attack against a creature it can reach. On a hit, the target takes 6d10 necrotic damage. The target must succeed on a DC 18 Constitution saving throw or the wielder of Apollyon regains hit points half to the total damage taken. If the target is reduce to 0 see Life/Undead/Celestial/Fiend Eater for results.

Erysichthon Curse. The wielder of Apollyon no longer can be satiated by food or drink. Though food and drink still keeps the body going it is tasteless and gains no nutritional value from it. The wielder can eat or drink anything edible to fuel the body of the wielder. Alcohol does not effect the wielder either. This also means that potions or poisons do not work on the wielder; and a magical potion taken will just lower the hunger levels of Apollyon and the wielder will gain no effects of the potion.

The hunger that comes from Apollyon is that of its need to consume energy, life or magical, and as the time goes on without the hunger grows until it is unbearable and it must feed. The wielder can go for a time without consuming energy for Apollyon  but as the hunger grows it begins to be harder and harder for the wielder to ignore. When the hunger gets to a certain level, the wielder is tipped over into a murderous hunger rage and attacked those around them until knocked unconscious or feeds on energy, when the hunger is satiated. Stress level can be tracked on a d100. 

In extreme stressful situations or at the start/end of combat the wielder needs to roll a d100 for a stress check. If that roll is under the current amount of stress points then the wielder makes a Wisdom Saving throw DC 18 to maintained control. On a fail save, the wielder begins to search for an energy/life force large enough to feed Apollyon and reduce the stress down to zero; that will cause the wielder to attack everyone and everything in range.

• The first 5 days without Apollyon eating the wielder accumulates 10 stress point; every day after that an addition point.
• If the wielder is in combat or combat is ended but no energy/life was consumed, add 10 stress points.
• Stress points can be reduced by consuming magic or life, depending on how powerful the magic is and/or what the life force is from will depend how many stress points is reduced. 
  • Small/Tiny size Life/Common Potions: -5 stress
  • Med Size Undead/Life/Uncommon Potions: -10 stress
  • Large Size Undead/Life/Other Potions: -15 stress
  • Fiend/Celestial: -20 stress.

Proficiency with a Whip allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Damage: Force, Bonus: Armor Class, For every level of 10 Hunger Stress Point reduce the max number of charges by 1 , Replaces an arm, Finesse, Reach, Slow