Swamp Bubble

You create a 5-foot-radius putrid swamp bubble that floats where you choose within 10 ft of you where you cast it. Once cast, the bubble remains inactive and gases stew within it for 1 minute. After then, any time a creature gets within 10 feet of the bubble, it bursts, creating a 20-foot-radius cloud of putrid gases that lasts for 1 minute.

Any creature in the cloud's radius when it bursts, as well as anyone who starts their turn in the cloud, must succeed a constitution saving throw or become Poisoned for 1 minute. A creature poisoned in this way must spend their turn leaving the cloud of gases. If a poison creature attempts to go through the cloud again, they must make a constitution saving throw, or are unable to walk into the cloud for that turn.