|The Empire, looking for a way to deal
with Rebel cell organizations genetically engineered an alien life form. The
Xenomorphs were bred as hunter / killers from the get go, created with acid
for blood and propensity for killing their enemy quicker than Ronto stew
through a Jawa the Empire thought that they had the answer to all their
They were wrong.
The Xenomorphs replicated quicker than anyone thought they would and nearly overtook the facility they were being housed in. Three separate ships were used to transport them: One was a capital ship that was lost via some sort of hyperspace anomaly. The second was a vessel that was targeted to crash land on a planet believed to be occupied by the Rebellion at the time, as it turned out the beliefs were right and the Xenomorph that survived the crash quickly found a host and replicated. The last vessel was intercepted by Rebellion forces and taken to a Rebellion weapon's testing facility where they passed along the message that they had discovered a new weapon that Empire was trying to develop. The Rebel high command lost contact with this remote outpost and dispatched the Mutt Squad to find out just what had happen.
What the Mutt Squad discovered was that the Xenomorphs had taken over the outpost and nearly succeeded in killing them to before the group was able to beat a hasty retreat and destroy the space station remotely. Not long after word of the remote Rebel base having gone offline came to the attention of Rebellion high command and once more they dispatched the Mutt Squad to discern just what was going on. As soon as they realized what had infested the base they quickly returned to their ship and turbo lasered the base from orbit.
The vessel that was lost due to the hyperspace anomaly was discovered when Mutt Squad hit an unstable wormhole during an attempted escape from Durga the Hutt. They burnt out their Hyperdrive and most of their fuel cells and were forced to dock with what they believed was a derelict vessel, they quickly found out just what was waiting for them on that ship and it was only through skill and cunning that they were able to escape with their lives.
Two other known encounters have occurred between the Mutt Squad and the Xenomorphs. Once when they traveled to the remote planet Filve, only to find it infested with the Xenomorphs. They rescued a Jedi Knight that had been trapped there and made their escape. The planet was quarantined and subsequently destroyed through planetary bombardment. The truth of what had happen to the Filvians finally came out when the Kae' Caballa faced off against Lady Lumiya and she revealed that she was breading the Xenomorphs for an attack on Coruscant. When the Filvian plot failed she moved operations to Hoth and was on the verge of completing her quest for revenge when she was slain by Kae'. As he stood over her body the eggs around him began to open and he used the Jedi pyrokinetic ability to destroy the menace of the Xenomorphs once and for all.
Since then there've been no more sightings of the Xenomorph, one could only assume that they've finally be destroyed.