Heliana's Guide to Monster Hunting, pg. 511
3rd ring Wyrd, Conjuration
Emanating from a point within range, a noxious, 20-foot-radius sphere of colourless fumes creates a choking, eye-watering miasma that penetrates through creatures’ skin.
When a creature enters the spell’s area for the first time on its turn or starts its turn there, it must make a Constitution saving throw. It takes 3d6 poison damage and becomes poisoned until the end of its next turn on a failure, or takes half as much damage and is not poisoned on a success. Whilst poisoned in this way, a creature has disadvantage on saving throws made to maintain its concentration.