Venom Strike

As part of the action used to cast this spell, you must make a melee attack with a light weapon against one creature within the spell’s range, otherwise the spell fails.  The target must make a Constitution saving throw against your spell save DC.  On a failed save, the creature is poisoned until the end of your next turn. 

At Higher Levels.  At 5 level, the melee attack deals an extra 1d6 poison damage.  The damage increases again by 1d6 at 11 level and 17 level.