The earth quakes, reality breaks, torn asunder by air.   You sing a discordant song infused with magical power. When you cast this spell, the vibrations you cause begin to distort reality in a 10-foot radius centered on you. Creatures you choose and unattended objects within that area take 2d6 thunder damage, and damaged creatures must make a Strength saving throw. If they fail, they are knocked prone.   As an action on each of your turns while maintaining concentration on this spell, you can strengthen your song, repeating the effect while increasing the affected radius by 10 feet and the thunder damage by 2d6 each time, and causing affected creatures you choose to make the Strength saving throw to avoid being knocked prone. The affected distance and damage cannot exceed an 30-foot radius or 6d6 thunder damage.