Blade Barrier

You create a wall of slashing blades. The wall can be up to 20 feet high and 5 feet thick, and can either be a straight wall up to 100 feet long or a ringed wall of up to 60 feet in diameter. The wall provides three-quarters cover and its area is difficult terrain. When a creature starts its turn within the wall's area or enters the wall's area for the first time on a turn, it makes a Dexterity saving throw, taking 6d10 slashing damage on a failed save, or half as much on a successful save.