Blue-frost Blade

As part of the action used to cast this spell, you must make a melee attack with a weapon against one creature within the spell’s range, otherwise the spell fails. On a hit, the target suffers the attack’s normal effects, and is temporarily charged with hypothermic frost. Until the end of your next turn, if the hit creature takes both an action and bonus action on their turn, or they take a reaction, you may deal 1d8 cold damage to them and end the spell. 

This spell’s damage increases when you reach higher levels. At 5th level, the melee attack deals an extra 1d8 cold damage to the target, and the damage the secondary target takes increases to 2d8. Both damage rolls increase by 1d8 at 11th level and 17th level.