After migrating to Mt. Heerbaun, Koffing could no longer rely on a steady stream of pollution. A mutation allowed some Koffing to develop a Fire typing to help extract more latent toxins for nutrients and a water typing to be able to spend more time underwater. Steam produced by Axyllian Koffing is virtually free of pollutants, and they are very often used in saunas to both clean the air and clear people's skin.
Axyllian Weezing's greater head stores water, while the second head filters it. This adaptation has actually resulted in a more efficient distribution of nutrients, resulting in a third, smiling head manifesting.