From Emperor's Hammer Encyclopaedia Imperia

Eos is Aurora Prime's only moon and it's also the home for the Dark Brotherhood. It is known to have no atmosphere or hydrosphere and it's main terrain is that of a crater field. It's temperatures are frigid, usually about -150° to -85°C.

It has light gravity and it's population is that of 750,000. It's day length is about twelve hours, while it's year is about forty-five days. Like Aurora Prime, it has an above-average technology level.

It's major imports are: All major necessities and materials, while it's major exports are: Minerals, ores.

It's ruled by an Imperial Governor (the Grand Master of the Brotherhood is the Governor) and a Theocracy-type government.