So the demons are thought to be native to solis, but one of my theories is that the meteor that crashed in the desert had demon eggs. The demons live in the jungle biome because they wouldn’t survive in the desert or that they moved to the jungle to feed on humans, so we know that the demons don’t eat animals but only humans that are useful to them, they eat the brains of the humans they are using, they are unable to leave the strange bubble because of the amount of oxygen that there is, my theory is that they live in a planet with little oxygen, that is why when Rico enters one of the bubbles he says “ Can’t breathe “ also when he leaves them he takes oxygen because of the lack of oxygen in these bubbles. If they were prehistoric, Rico would be able to breath without any problem because there was way more oxygen than before