You infuse a willing creature’s weapon with elemental power. Choose cold, fire, lightning, or nature. Until the spell ends, the weapon deals an extra 1d8 damage of the chosen type. If the weapon already deals damage of that type, it instead deals an extra 2d8 damage of that type.   Additionally, whenever the target scores a critical hit with the imbued weapon, the target of the attack must succeed on a Wisdom saving throw or be stunned until the end of its next turn.