Astral Barrage

You create a portal to the cosmos and send asteroids hurtling through it. A creature of your choice that you can see within range must succeed on a Dexterity saving throw or take 7d6 bludgeoning damage. You can use an action on subsequent turns to keep the portal open and target another creature, which must make the same saving throw. The spell ends if you use your action to do anything else. While concentrating on this spell, your speed is halved.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, larger asteroids fly through the portal, and the damage increases by 2d6 for each slot level above 3rd.