A creature you touch has resistance to acid, cold, fire, force, lightning, and thunder damage until the spell ends. If the spell is used against an unwilling creature, you must make a melee spell attack with a reach of 5 feet. If the attack hits, for the duration of the spell the affected creature must make a saving throw using its spellcasting ability whenever it casts a spell that deals one of the given damage types. On a failed save, the spell is not cast but its slot is expended; on a successful save, the spell is cast but its damage is halved before applying the effects of saving throws, resistance, and other factors.