Thunderous Stampede

You throw out a horseshoe, and when it strikes the ground numerous projections in the shape of wild horses appear and charge ahead, forming a line 60 ft long and 10 ft wide. A creature caught in the stampede must succeed on a Dexterity saving throw or take 3d8 thunder damage and 2d8 magical bludgeoning damage and be pushed 10 ft away from you and be knocked prone. If a creature succeeds on this save, it takes half as much damage and is not knocked prone or pushed.