Cosmic Fury

When this spell's concentration ends, you shoot out a dark cone filled with small stars that damage those hit by them. The cone has a length and radius of 15 feet and grows by another 15 feet for every round this spell was concentrated on for. Creatures within the cone the moment concentration is broken must make a Dexterity saving throw. On a fail, the target takes 6d6 radiant damage, plus an additional 2d6 radiant damage for every round this spell was concentrated on for, or half as much on a success.