Demi

You tear a hole in the space above you, leaving a void that emanates entropic energy. This void follows you for the duration. When you cast the spell, choose up to 3 creatures within 15 feet of you. The creatures you designate must make a Constitution saving throw, or take a number of d10's equal to a quarter of their hit dice in force damage (rounded down), with a minimum of 6d10. On a successful save, creatures take half damage and cannot be reduced to 0 hit points by this damage. On each of your turns until the spell ends, you can use your action to damage creatures in this way again, targeting the same creatures or different ones as long as the creatures you target are within 15 feet of you.

At higher levels. When you cast this spell using a spell slot of 7th level, the number of creatures you can target increases to 4. When you cast this spell using a spell slot of 8th level, the number of creatures you can target increases to 5. When you cast this spell using a spell slot of 9th level, the number of creatures you can target increases to 6, and the number of d10's rolled is increased to half the target creature's hit dice.