Dragon Fist

You unleash a serpentine draconic spirit that coils through the air and lashes out at every creature of your choice within a 60-foot cone originating from you. The targets must make a Strength saving throw. On a failed save, they take 2d8 radiant damage and are knocked prone. On a successful save, they take half as much damage and are not knocked prone. When you cast this spell, choose one creature within the cone to be the target of the spirit. If this creature fails its saving throw, they take an additional 12d6 piercing damage and are subjected to a second effect as the dragon rushes forward and strikes them with legendary power.

Rush. If the target is Large or smaller, they are pushed up to 100 feet away from you in a straight line. If the target strikes a surface, both the surface and the creature take 1d6 bludgeoning damage for every 10 feet the target was pushed. If the surface were to break, the dragon continues beyond the surface and the damage resets.

Explosion. If the target is huge or larger, the spirit entangles them and implodes into a devastating wave of radiant energy. The target immediately takes 6d6 radiant damage, or 8d6 if they are gargantuan.