Booming Rune

You form a glowing rune upon a solid surface of your choice within range that you can see. The rune remains there for the spells duration.

Upon casting this spell or as a reaction on a later turn, you can trigger the rune to cause it to explode into a thunderous wave. Any creatures within a 10 foot cube centered on the rune must succeed a Constitution saving throw or take 1d6 thunder damage and be knocked up to 5 feet away from the rune.

After the rune is triggered the spell will end. 

This spell's damage increases by 1d6 when you reach 5th level (2d6), 11th level (3d6), and 17th level (4d6).