[@Jeyma] Your specific scenario I'm iffy about (sorry for forgetting to mention) for a couple of reasons. First is me wondering why am oxygen intolerant alien would inconvenience himself by joining a band of majority oxygen dependant aliens. Secondly that the Nova Dawn is an ancient relic, and would probably be a bitch to accommodate your character's specific needs if it was at all possible. Thirdly is I'm hesitant to go deep enough into "real" science to specify chemical elements such as oxygen, as opposed to classical elements like fire, air, etc.

Maybe something like an amphibious fishman that needs a rebreather would be more palatable.