Blitz (5e Equipment)
From D&D Wiki
Weapon (dagger), rare (requires attunement)
A rather sharp dagger, laced with bright yellow runes of speed. In a pinch, the wielder can activate these runes and release a flurry of blows so massive they blot out light. You have a +2 to damage rolls made with this weapon
When you take the attack action, you may forgo any amount of your modifiers to damage for this weapon until the start of your next turn, to a minimum of 0. When you do so, for every +2 you sacrifice, you may make an additional attack with Blitz. Spells and other effects cannot change the modifier or add dice to these additional attacks.