Koros is tidally locked with Yridia II, the same side always facing the planet. Without an insulative atmosphere, the dark side is much colder than the starlit side. Formerly the home of House Cestus, this moon became abandoned after an outbreak of undead. While some facilities underground remained, most of the surface installation was destroyed in the orbital bombardment when the complex was closed. The moon was re-opened as a Tarentum stronghold when the old Cestus Complex was destroyed, and House Cestus was re-opened, with the wreckage of the VSD Corsair becoming the House's new headquarters and stronghold. Koros now has regular traffic opened up to it once more, though all traffic must still be cleared through the Aegis platform beforehand.
Contrary to rumors, the undead infestation upon the moon of Koros was not Draugr, but actually Aptrgangr. Only a few Draugr existed upon the moon. After the destruction of the old Cestus Complex, it is unknown how many of the undead residents may have survived.