Patavig is the second of the Macedon system's giant terrestrial planets, and by far the more interesting. Most of the surface is covered by a vast sea of liquid ammonia, in which a unique aquatic ammonia-based biosphere has developed. While the frozen continents are largely bereft of life, a rich bounty of complex organisms — many larger than a human — flourish in the chilly, toxic seas.
While dreadfully inhospitable to humans, Patavig is suitable for colonization by the volus. Negotiations between the Systems Alliance and the volus' patrons, the Turian Hierarchy, have made good progress.
For some reason, the planet info gives the temperature as −130 °C, which is approximately 50 degrees below the ammonia melting point, making an ammonia ocean (or ammonia based biochemistry) extremely unlikely. Also, the combination of the low luminosity of the star, and the planet's distance from it, mean that it only receives 10−4 of the radiation Earth does, making even that temperature unlikely as well.
- If the asari-led Council dies in Mass Effect, Patavig was granted to the Vol Protectorate in exchange for volus support in a key human-led Council vote in 2183. The Alliance's Fifth Fleet visits the planet in 2185 during its cruise of the Attican Traverse.
- In 2186, the anti-conspiracy activist Bernard Plim claims to have exposed "the Alliance funding of the Volus Mafia" on Patavig.