Dagger of Negation

Weapon (dagger), very rare (requires attunement)

This short, grooved, leaf-shaped blade is inlaid with silver and adamantine and is treated as a weapon of both metals for the purpose of bypassing resistance to attacks.

The wielder gains a +2 bonus on attack and damage rolls with it. In addition, if the target has resistance to one or more types of damage, it loses one of those resistances (choose randomly) for 1d4 rounds unless it succeeds on a DC 16 Charisma saving throw. The wielder knows what form of resistance was suppressed.

If the target is hit more than once, choose an additional type of resistance randomly; if the target has only one form of resistance, the duration it is suppressed is instead increased by 1d4 rounds. Bludgeoning, piercing, and slashing are each considered a separate type of damage for this purpose, but each includes all types of weapons that bypass that resistance (such as silvered, magical, or adamantine weapons).

If the hit is a critical hit, the wielder is immediately aware of all resistances the target has and can choose which resistance the target loses on a failed save, and the target has disadvantage on this saving throw.

If the target has magic resistance, the wielder is aware of this upon scoring a hit and can choose to target this resistance rather than one of the target’s other resistances, even when it is not a critical hit. A failed save suppresses the target’s magic resistance for 1 round.