Cloud of Atrophy

Uttering the final ghastly words of this incantation, the pendent emits a cloying, black mist run through with an eerie, ghostly light.  The fingers of the vapor crawl along the ground away from where you are standing to form a hungry cloud that moves at your direction.

This spell creates a 20-foot radius sphere of mist--the interior of which is considered heavily obscured--centered on a point within range.  When the spell's area overlaps a creature for the first time on a turn and at the start of each of your turns, that creature takes 4d10 necrotic damage and immediately suffers 2 levels of exhaustion.  A successful Constitution saving throw halves the damage and negates the exhaustion for that round.  Creatures that begin their turn alive outside of the cloud's area begin healing exhaustion levels at one level per round until they are restored to where they began before they entered the cloud.

Each round, as an action, the caster can cause the cloud to move 15 feet in any direction up to the maximum range, rolling along the surface of the ground. The vapors slither along the lowest level of the land, even pouring down openings.  The cloud is more ethereal than physical in nature, and therefore cannot be dispersed by strong winds or similar effects.  Creatures are affected even if they hold their breath or don't need to breathe, but undead or constructs are immune.

Control of such potent energies is tenuous at best.  If the caster's concentration is broken in any way except by their own willing dismissal, the spell collapses back to its point of origin.  In such an event the pendent focus shatters, consumed by the spell, and the caster must save against their own spellcasting DC or suffer one level of exhaustion for every round they spent concentrating on the spell.  If this does not immediately kill the caster, resulting levels of exhaustion must be healed as normal.