Artifact Weapon (Dagger), Finesse, Light, Range (20/60), Thrown, Requires Attunement

• Gives a +3 to all attack and damage rolls made with this magical weapon
• Deals extra 2d6 necrotic damage 

Unhealing Wounds: When you hit a creature with an attack made with this weapon, the target loses maximum Hit Points equal to the amount of damage dealt until this is cured by the Greater Restoration spell. 

• Wounds done by this weapon do not naturally heal, and leave behind black open scars that cannot be removed by anything except for the Wish spell.
  • Creatures with these wounds or scars lose extra 1d6 Hit Points each time they take psychic or necrotic damage

Corruption: Touching a sleeping creature that wasn’t put to sleep by magical means with the tip of the dagger turns their dream into a nightmare during which their mind becomes exposed to horrifying eldritch powers from beyond.
They must make a DC:16 WIS saving throw and if they succeed, they are immune to this effect for one week. On a failed saving throw, they wake up as a puppet of the wielder and of the eldritch entities.

• The affected creature will be utterly loyal to the wielder and will do even suicidal tasks. They will not remember anything they had done in this state once the effects end.
• Once per day, the affected creature can subconsciously try and break free from the effect, this is a DC:20 WIS saving throw.
• The effect ends if the wielder loses attunement, or if they die.
• Affected creatures can be cured by the Greater Restoration spell
• Once the effects ends, all the creatures that were affected must make a DC: 8 WIS saving throw every night for one week. If they fail, they become controlled by the dark eldritch gods, and they go on a murderous spree for 12 hours.
• If a creature of CR 5 or lower fails on the saving throw, there is a 25% chance that they permanently transform into rampaging Abberations of CR 1-10, decided by a dice roll.
• If a creature of CR 15 or Higher fails on the saving throw, they are not fully under the control of the wielder, but they are charmed by them and consider them a trustworthy ally or advisor. The wielder also becomes capable of telepathically communicating with them for as long as the effect takes place.    

You also gain the ability to cast the Dream spell at will, but only being able to affect a single creature once until you finish a long rest. 

Infestation: Killing a creature with this dagger causes it to start transforming and growing various limbs, tendrils, growths, and generally malforming the entire body. After one hour the body returns back to life with its original stats and abilities, but with the Aberration creature type, chaotic evil alignment, and with their only purpose being to kill. Creatures killed by this newly formed abomination became themselves an abomination as well. (This abomination is not loyal to the wielder, but will attack neither them nor those under the effects of corruption).

CURSE (For GM only!)

After a day in their possession, the wielder of this dagger starts hearing indiscernible whispers in their head, these whispers will get louder with passing time.

After three days of possession, the wielder’s perception of reality will change, they will start having hallucinations, with people seeming like malformed, twisted beings with various growths and tentacles coming out of their body. They will also start seeing gargantuan eldritch entities enveloping the world or the sky (moon).

From the seventh day forward, the wielder must make a DC 15 wisdom saving throw each night until they fail or get rid of the item. If they fail, they lose their sanity and their alignment changes to chaotic evil. They start worshipping the eldritch entities and they start to understand the whispers, which will command them what to do.

(They are generally able to stay the same, and they will try to hide their new allegiances from others, so they will act like normal, but if an entity commands them to do something, they have to, failing to do so can have various severe consequences I leave up to you)

(Warning for GM, using this item in your game might cause severe derailment and the corruption mechanic can make your characters quite broken, and you have to be prepared for it. I recommend building a plot point behind the dagger, so your players know there is something wrong with it. If you decide to use this item as random loot, then I applaud your bravery and penchant for chaos)