Sword of the Serpent
Weapon,
Very Rare
(requires attunement; cost 45000 gp)
Crafting Components
Unique (uncraftable)
You gain a +2 bonus to attack and damage rolls made with this magic sword. When you hit with this weapon, you deal an extra 1d6 poison damage. The sword has 3 charges and regains all expended charges at dawn.
While wielding the sword, you can use an action to expend 1 charge and cast polymorph on yourself, transforming into a giant poisonous snake . While in this form, you retain your Intelligence, Wisdom, and Charisma scores.
Source