Source: Critical Role

Weapon (dagger), ??? (requires attunement)

The dagger has a hooked, dark metal blade that is cold to the touch. A faint black energy drifts off the edge of the blade.

The dagger has a +1 bonus to attack and damage rolls. The user can also spend one of their hit dice to deal an additional 3d6 necrotic damage on a hit.

Curse. The dagger is cursed, so that the wielder bound to it wants to remain bound to it and feels a compulsion to keep it with them. When the wielder is magically healed, they must spend a hit die to regain hit points. If the wielder has no hit dice to spend, they immediately die.