Elemental Barrier

This spell creates a square barrier 10 feet wide, and up to 30 feet away facing in whatever direction you choose. Any attack or spell that deals Fire, Acid, Lightning, Cold, or Thunder damage that would have to pass through this barrier has its damage reduced by 1/2 and causes either Disadvantage on attack rolls on creatures which are behind the barrier, or granting those protected creatures Advantage on their saving throw to resist the damage. 

At the start of each of your turns you can move the location of the barrier by up to 30 feet in any direction.