Campaign: Dungeons of Drakkenheim
Researching the Spell: A character who can cast 5th level spells can research Conjure the Deep Haze. To complete the research, the caster must spend 10 days of downtime and 500 gp.
Contaminated Spell: When you cast this spell, you gain one level of contamination.

  You create a 20-foot-radius sphere of the Deep Haze on a point you choose within range. The fog spreads around corners. It lasts for the duration or until strong wind disperses the fog, ending the spell. 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 must succeed on a Constitution saving throw. On a failed saving throw, it suffers 8d6 necrotic damage and gains one level of contamination. On a successful save, the creature takes half as much damage and does not gain any contamination levels. Creatures are affected even if they hold their breath or don’t need to breathe.