Air of Syphilis

5ft cub of yellow swirling mist. Any creature inside the cube takes 1D6 necrotic damage at the top of every round they stay in the cube.

the creature must also make a constitution saving throw; on a successful throw the creature gains no effect, on a failed one the creature gains the poisoned effect. This effect lasts until the spell ends or is dispelled, alternatively it can be removed by the creature using its action to make another constitution saving throw.