Oxygen is the second-in-command of the MPA and takes over if Xenon isn't there. She can tell you what enemies you're facing as well as tell you their specific weaknesses.

Hydrogen has undergone a freak accident, causing him to gain upgrades from enemy remains, but if he takes too many, he'll transform into a savage beast with no means of determining what's right or wrong. Only Oxygen knows of his condition and shares a personal communication link to guide him through his predicament.