The self-styled "Emperor" Andross was a massive, Force-sensitive creature, possessed of an appropriately-massive brain and an ego to match. He envisioned himself as the ruler of the Lylat sector, located on the far side of the galaxy, and would do anything to take over the star systems located therein. He was able to amass a significant number of weird as hell powerful starfighters, warships, and ground vehicles, but that wasn't enough. During the course of his campaign to take over the sector, he developed a number of bio-weapons; huge monstrosities, they ranged from giant clams to sun-loving...things.
As Andross established his power-base, the Star Fox Team, consisting of Amaran fighter pilot James McLeod, along with his teammates Peppy Hare and Piggy Hogbreath, were tasked with gathering intelligence on the threat posed to the sector capital, Corneria. Betrayed by the snot-nosed pig, the team was captured; the Lepi Peppy barely managed to escape to inform the authorities. The big galoot used this as an excuse to begin his reign of terror over Lylat. Staging from the smoggy, decrepit world of Venom, he soon conquered Zoness, Aquas, Macbeth and Titan. By the time James's son Fox had completed his own training as a pilot, the forces of Andross threatened Katina, Fortuna, and even Corneria itself. In the brutal campaign that followed, the unreasonable brute was blown up with the rest of his shitcan base.