Known as the starcraft cemetery, Korlus was the regional toxic junk yard for centuries. Ships reaching astronautical "near-death" at connecting mass relays were sent to Korlus, stripped of every useful component, then dumped planetward to clear shipping lanes.
Currently Korlus hosts numerous merc factions such as the Blue Suns, rumored to be using downed ship fossils to test advanced munitions. Massive gun batteries threaten anyone attempting planetfall, with minimal defenses against ground attack.
Because ancient vulcanism greenhoused the planet, Korlus was too hot and CO2-rich to develop a biosphere, despite the abundant lakes that could have sponsored the development of life.
Now cool enough for protected habitation, but too scorching for anyone but extremophiles and mercenaries seeking secrecy, Korlus supports numerous krogan outposts. The krogan have therefore seeded Korlus with hardy varren, often kept as war hounds. Varren live primarily on a diet of geophagous vermin and each other.