The Abyssal Dagger’s origin is unknown however those that attune to it successfully hear strange noises and some even become entangled in shadow. The misty tendrils seem to influence the wielder to kill and to maim all creatures. 

Attacks:

Splice: 1d10 slashing + 2d10 necrotic damage and creature takes an additional 2 slashing damage per turn for 5 rounds (once per short rest)

Slash: 1d10 piercing + 2d10 necrotic damage 

Abyssal Strike: 1d10 piercing + 5d10 necrotic + 4d10 fire damage (once per long rest)

shadow tendrils: 8d10 necrotic damage (range 40 - 120ft) (once per long rest) 

Buffs And Debuffs (only available when attuned)

Tendrils Of Madness: once a creature attunes to the dagger the dagger begins to whisper to you, urging you to kill everything, after you kill 10 - 15 people (depending on your alignment) the DM takes control of the creature and attacks anything near that creature (friends and allies included) 

Voice Of The Darkness: if the creature dies while using the dagger, a strange voice will tell you “it’s not over” (or something close to that) and is True Resurrected as well as deals an additional 10d10 necrotic damage to all attacks with the dagger, however they also gain the effects of Tendrils Of Madness and the creature will fall unconscious 10 rounds later.

Ancient Power: the creature wielding the Abyssal Dagger gains advantage on all attack rolls and saving throws against all creatures except Aberrations and infernals in  which case the creature gains disadvantage on attack rolls and saving throws against them. When attacking creatures that you have advantage on you give them disadvantage on attack rolls and saving throws for 4 rounds.

 

 

 

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

Notes: Immunity: Bludgeoning, Piercing, and Slashing from Nonmagical Weapons, Abyssal Dagger - requires attunement by a Warlock, or wizard., Finesse, Light, Thrown, Nick