Astral Storm

A livid streak of translucent starry energy rends open the fabric of space and time, light spilling out from the growing rift centered on a point you can see and spreading to a radius of 360 feet. Plasma from incompatible elemental structures arcs out, thunder booms, and astral tides and gales roar forth. Each creature under the cloud (no more than 5,000 feet beneath the cloud) when it appears must make a Constitution saving throw. On a failed save, a creature takes 2d6 Radiant damage and becomes blinded for 5 minutes.

Each round you maintain concentration on this spell, the storm produces different effects on your turn.

Round 2. The unearthly light begins to wither creatures inside it. Each creature and object under the cloud takes 1d6 Necrotic damage.

Round 3. You call six bolts of plasma from the rift to strike six creatures or objects of your choice beneath the cloud. A given creature or object can't be struck by more than one bolt. A struck creature must make a Dexterity saving throw. The creature takes 5d6 Lightning and 5d6 Fire damage on a failed save, or half as much damage on a successful one.

Round 4. The extraplanar light intensifies even further, with creatures' bodies having toxic reactions to it. Each creature under the cloud takes 2d6 Poison damage.

Round 5–10. Solar gales and unthinkably cold astral tides assail the area under the rift. The area becomes difficult terrain and is heavily obscured with bright light, which extinguishes any and all darkness within it. Each creature there takes 1d6 Cold damage. Ranged weapon attacks in the area are impossible. The tides and light count as a severe distraction for the purposes of maintaining concentration on spells. Finally, gusts of astral wind (ranging from 20 to 50 miles per hour) automatically disperse fog, mists, and similar phenomena in the area, whether mundane or magical.