This planet was always the worse world due un-breathable atmosphere, no oxygen, dark surface because of big smog pollution that keeps much of the light too, space junk and ocean brutally toxic. The natural landscapes in venom, are: wastelands, canyons, rocks and temple ruins of Lost Tribe of Cornerus before being Andross's base.
Venom was the Andross' prison by General Pepper because of his disobedience which destroyed the large portion of Corneria City by his secret dangerous experimentation. For 5 years isolation to die, this wasted planet became the Andross' empire where is all controlled by his mind, army formed and civilizations created for him.
Before of Lylat Wars, this planet is invaded by Star Fox led James McCloud for investigate and reports the strange activity to be attacked by Andross caused for Pigma Dengar's betrayal. When Andross declare war against Corneria, this planet is invaded again by Star Fox led Fox McCloud this time for destroy Andross and his army.
With end of wars and Andross demise, the new tyrant called Anglar Emperor and his amry take care of this planet became enemy world of Corneria. After of Emperor Anglar and his army destroyed by Fox McCloud, Venom is totally clean thanks for Dash Bowman that used his grandfather's terraforming device and same became good ruler this planet starting the original goals of his grandfather.