Sword Tunnel

You stretch the space in front of you, summoning two rows of swords that rush inward from one end of a 10-foot-wide, 90-foot-long corridor. A narrow gap between the blades shifts and weaves through the corridor. When a creature enters the corridor for the first time on a turn or starts its turn there, it must make a Dexterity saving throw. On a failed save, it takes 8d10 slashing damage. On a success, it takes no damage. The gap moves 20 feet at the start of each of your turns.

When you cast this spell using a spell slot of 8th level or higher, the corridor twists into a nightmarish, spinning vortex. The gap still moves, but the save is made with disadvantage, and on a failed save, a creature is restrained by the twisting blades until the end of its next turn.

When you cast this spell using a spell slot of 9th level or higher, the blades move too fast to dodge normally (simulating reduced invincibility frames). The damage drops to 4d10 per hit, but the blades strike repeatedly: a creature in the corridor automatically takes the 4d10 slashing damage at the start of its turn and whenever it moves, with no saving throw allowed.