Cernunnos

Mass Effect 2
Cernunnos is a sizable gas giant with a hydrogen-nitrogen atmosphere. It is believed to be an extrasolar capture due to its close stellar location. In a rare phenomenon, it is near enough to its red dwarf star to be within the life zone, though its massive size prevents the tidal lock that usually occurs at such a range. While nothing could survive on the surface of a planet with such crushing gravity, Cernunnos' moon Caleston is habitable. Cernunnons is skimmed for its abundant hydrogen, and refineries on Caleston process it into a metastable metallic form for use as starship fuel.

Mass Effect 3
Cernunnos is a sizable gas giant with high nitrogen content. It is believed to be an extrasolar capture due to its close stellar location. In a rare phenomenon, it is near enough to its red dwarf star to be within the life zone, though its massive size prevents the tidal lock that usually occurs at this range.

While nothing could survive on the surface of a planet with such crushing gravity, Cernunnos' moon, Caleston, has life. Cernunnons was skimmed for its abundant hydrogen, and refineries on Caleston processed it into a metastable metallic form for use as starship fuel. The Reapers have since destroyed the operation.