I'm kind of on a journey in search of how to scientifically explain fantastic creatures in a way that doesn't rely on magic, because I think that makes things more interesting. Currently my biggest challenge is with the flyers, especially the 6 members. Most of the answers are saying that it is impossible, others even say that it is possible, but it would not be possible for a human to assemble and it would be necessary to change the atmosphere and gravity of the planet where they live. Thinking about it I remembered that I saw a post about dragon breath right here on the WBSE, one of the answers was about the dragon expelling a gas that would ignite when coming in contact with the air, this gas would be light and help the dragon to fly better, but after the breath was used, the dragon would become heavy and could not fly until it refueled.
Based on this, the question came to me: is it possible for an animal to produce a light gas that helps it to fly when flapping its wings and in which part of the body would this gas stay? Is it possible to produce this gas by eating meat(dragons, griffins) and plants(pégasi)? In the case of dragons, the gas would not be used to attack as part of the breath, I already have an idea of something else for the breath
A gas that the animal can produce from feeding or perhaps even breathing. Ah, the animal must be able to carry someone, a rider. My world is similar to Earth(not venus) but with an atmospheric density twice as high as, according to my research, nitrogen makes flight easier and oxygen allows for the existence of larger flying animals. In my world these animals (pégasi, dragons, griffins...) are created, they didn't arise from evolution.