Eldritch Cataclysm

You gather the raw essence of eldritch power and focus it into a devastating force. A massive beam of crackling energy streaks forth from your outstretched hand, reaching toward a point you designate within range. As the beam connects with its target, a swirling sphere of chaotic energy forms at the end of the beam, resembling a gathering storm.

The beam extends in a straight line for up to 240 feet. Each creature in the beam's path must make a Dexterity spell save. On a failed save, a creature takes 12d10 force damage, is pushed 60 feet in the direction of the beam, and knocked prone. On a successful save, the creature takes half as much damage and is pushed 30 ft, but isn't knocked prone.

Upon completion, the sphere erupts into an explosion of chaotic energy, unleashing a cataclysmic wave of destruction in a 60-foot radius sphere centered on the target point. Each creature within the area must make a Dexterity spell save. On a failed save, a creature takes 14d12 force damage and is pushed 60 feet away from the edge of the sphere and knocked prone. On a successful save, the creature takes half as much damage, is pushed to the edge of the sphere, and isn't knocked prone.

For each creature that dies as a result of the Eldritch Cataclysm's damage, the spell's damage increases by 1d10 to both the beam and the explosion, to a maximum of an additional 20d10. This increase lasts for the duration of the spell.