Ultimate Implosion

A 20-foot-radius sphere of your dragon's element is centered on yourself. The sphere remains for the spell’s duration. Each creature in the sphere when it appears or that ends its turn there must succeed on a Dexterity saving throw or take 5d6 damage and 2d6 of the element of the players dragon color. The sphere’s space destroys the terrain around it.

After the spell you take half the damage taken from the destruction of your spell. Creatures within 25-ft have instant disadvantage on their saving throw. Every creature that gets caught within the implosion takes 2d6 knockback damage and is launched 20-ft backwards. 

At Higher Levels: does an extra 1d6 for every level your character is.