Doomtide

You create a 20-foot-radius Sphere of inky fog within range. The fog is magical Darkness and lasts for the duration or until a strong wind (such as the one created by the Gust of Wind spell) disperses it, ending the spell.

Each creature in the Sphere when it appears makes a Wisdom saving throw. On a failed save, a creature takes 5d6 Psychic damage and subtracts 1d6 from its saving throws until the end of its next turn. On a successful save, a creature takes half as much damage only. A creature also makes this save when the Sphere moves into its space, when it enters the Sphere, or when it ends its turn inside the Sphere. A creature makes this save only once per turn.

The Sphere moves 10 feet away from you at the start of each of your turns.

Casting as a Circle Spell. Casting this as a Circle spell requires a minimum of five secondary casters. In addition to the spell's usual components, you must provide a special component (a string of three black pearls from Pandemonium), which the spell consumes. The spell's range increases to 1 mile, and its duration increases to until dispelled (no Concentration required). The spell ends early if any caster who participated in this casting contributes to another casting of Doomtide as a Circle spell.

When the spell is cast, each secondary caster must expend a level 3+ spell slot; otherwise, the spell fails.