Quick question: I just ran a session with level 3 PC’s in which I used Gas Spores. They are listed as CR 1/2, but the con save for preventing the poison damage (A whopping 3d6) and a death timer is 15. Why is such a potent effect listed at such a low CR? Gas spores are a very swingy thing to encounter. You could easily avoid their damage entirely, and the damage is only a danger at low levels.

— Jeremy Crawford (@JeremyECrawford) December 15, 2017

It's low CR because it has a high likelihood of harming no one.

— Jeremy Crawford (@JeremyECrawford) December 15, 2017