Dread Mist

You breathe out a 30ft radius sphere of thick smog that roils with the horror-stricken faces of the damned centered on a point you choose within range. The smog spreads around corners and lasts for the duration, is unaffected by wind and its area is heavily obscured.

When a creature enters the spell's area for the first time on a turn or starts its turn there, that creature makes a Wisdom save, becoming Doomed on a failure. A creature Doomed this way is also frightened, and while it remains in the smog, it takes 10 necrotic damage at the start of each turn. When a Doomed creature ends its turn outside the smog, it can repeat its save, ending the effect on a success.

If a humanoid dies while Doomed and within the smog, there's a 1/3 chance that a Specter rises from its corpse at the start of your next turn. The Specter purses the closest creature to it.

The smog moves 10ft away from you at the start of each of your turns, rolling across the ground after which its radius expands by 5ft to a max of 150ft. The vapours, denser than air, sink to the land's lowest point, pouring down openings.

Doomed: A doomed creature can't regain or have temporary hit points. The creature has disadvantage on saves against damaging effects. Typically effects that inflict doom come with the ability to end the condition or inflict the condition for a limited duration. For those who want to get rid of it quickly or are afflicted with a permanent form, a Greater Restoration or similar can remove Doomed.