Accursed Stinger

You morph the body of a willing creature in range, manifesting a stinger in the shape of the tail of a scorpion or the head of a snake out of part of their body. For the duration, the creature can attack with the stinger once per turn as an attack made with the Attack action. The attack is a melee spell attack, uses your spell attack bonus, and deals 3d10 poison damage on a hit. Additionally, the target of the attack must make a Constitution saving throw on a hit. On a failed save, the target is also poisoned until the start of the morphed creature's next turn. While poisoned, the target has disadvantage on Dexterity saving throws and treats all movement as though it is through difficult terrain.