Bramblebriar

Weapon (scimitar), legendary (requires attunement) While holding this scimitar, you can use a bonus action to activate its brambles. When you do, several barbed vines coil around its crossguard, over your wrist, and dig into your flesh. At the start of each of your turns, it drains 2 hit points from you to empower its poison. While attached to you in this way, you can’t be disarmed by normal means, and you are resistant to poison damage and immune to the poisoned condition. Each time the weapon drains your hit points, it gains one charge, to a maximum of 5 charges. The weapon continues to drain your hit points while fully charged. On a hit, its vicious barbs lash out from the scimitar and rake your target with venomous brambles, expending all charges within its vines. The creature must make a Constitution saving throw with a DC equal to 10 + your proficiency bonus. On a failure, the creature takes 1d4 poison damage for each charge spent. If you stow the weapon without expending all of its charges, the poison courses through your veins as you release the hilt and you must make a successful Constitution saving throw or take the damage from its thorns for each remaining charge.