Dagger of Death's Hand (5e Equipment)
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Weapon (dagger), legendary (requires attunement)
Hidden Hand. When you attack and hit a creature in the first round of combat or if the target can not see you, it must make a DC 19 Constitution saving throw. On a failed save, the target takes 4d6 necrotic damage in addition to the normal damage from the attack, or half as much damage on a successful one. You can use an action to teleport within 5 feet of a target up to 20 feet away or a target in dim light or in darkness. If you do so, you can use a bonus action to attack with this weapon.
Second Shadow. When holding this dagger in your hand, you may use a bonus action to make a copy of the dagger in your other hand so long as there you're holding no other items in that hand.