We all think we know what's best for Aliens and Predators. If Fox knocked on your door and asked you to pen canon, what would it look like?
PredatorThe Yautja are a race of space-faring game hunters who cruise the cosmos for deadly monsters to stuff and mount on the walls of their sweeeet rides. The Yautja's society is fiercely clan-based, with literally thousands of varyingly sized interstellar tribes playing a savage game of one-upPredatorship. Each tribe commutes to the next hunt in their own rockin' spaceship, handed down through possibly hundreds of generations. Each clan has their own
oh-so-special twists on the ritualized slaughter that almost every Yautja partakes in.
Your standard Predator, packin' exotic weapons and exotic scars. Lanky, slimy, leathery. Keeping it together for 'em are the Hish (I like the word). These Predators are the ipso facto enforcers of all that is 'The Hunt.' The Hish operate the happenin' hangouts we might call Motherships. Every Predator finds his way to one of these joints sometime or another; whether it is to brag, acquire spare parts or access new weapons. Keeping things as orderly as things can conceivably be when Predators are involved, the Hish have their work cut out for 'em. These adjudicators are unique.
The Hish pluck young promising Yautja from their clans and raise them to be swift, fair arbitrators between tribes and brutal defenders of the 'The Hunt' against outsiders. To be chosen to serve among the Hish is a terrific honor. These warriors are always on call; Hish pursue the most dangerous Bad Bloods, contain the worst outbreaks of the extragalactic disease we call the Alien, investigate and improve new technology, wage war, and settle disputes between
multiple clans that grow
too deadly. Ironically, the Hish are unable to engage in 'The Hunt' that they are honor-bound to protect. For them, this mystifies its spiritual underpinnings and they come to revere it so that they can almost be seen as a sort of faux-cult.
Specifically, the Shogun commander guy roarin' up there is what I imagine the standard Hish Predator-dude to look like. I have to admit I like the Halo-Predators too. When any Predator hangs enough trophies or accumulates enough honors amongst its fellows, it usually rises to a position of clan or Hish leader, but sometimes these grizzled vets instead choose to head home, literally. To reside on the Predator homeworld, on the ancestral lands of your clan, is one of the highest honors in the Yautja society. Many never even actually see this place, but this doesn't detract from the outright zeal they have for it. A special contingent of Hish maintains close watch over it and the solar system it's in. Terrestrial Yautja are uniquely independent and free to do as they wish, but still generally keep in close contact with their clan.
Predator homeworld on an overcast day. Oh, and for God's sake, the tendrils on their body aren't hair, they're just the weird equivalent of hair to Humans; they're just oily tendrils!
AliensThe sentient disease from outer-friggin'-space we call the Alien begins with the Space Jockey race. These extragalactic geeks are definitely the smartest folks anybody knows of in the year 2800. And they've basically been dead for millions of years. The Space Jockey's were (and are, if we consider the unsustainable bit o' population that remains) the apex of sentience. Mastering biology and engineering, the Space Jockey's made the next logical step and combined them. This synergism of opposites gave the Jockey's a step up on its Universal competition and they've been on top of the heap, in terms of outright braininess, ever since. The culmination of this fact is an impossibly complex 'biomechanical terrain' they developed – a symbiote. This strange substance, complete with a nervous system and encapsulating primitive intelligence, could bond with the equally self-modified Jockey's physically and mentally, giving them total awareness of the presences and thoughts of others anywhere within the limits of the artificial landscape. Soon, the ambitious Jockeys endeavored to terraform entire planets with it and synchronize with what would essentially be a sentient world.
Smart goop.Churning out the stuff on that scale would require a whole different method of production.
So the Jockeys manufactured the perfect delivery system (after a lot of tries). These factories could consume organic material to fuel the production of the symbiote. Once produced, the factory could interface with its product and do basically what amounts to a global landscaping gig. Modeled after both viruses and parasites for efficiency, the delivery system acquired the traits of the native life forms to better survive the harsh environments in would likely encounter. It was also designed for rapid mutation to quickly adapt to changing circumstances and to combat forces hostile to it. We would come to know these creatures as the Aliens.
... But there was a ghost in the machine. Turning the Aliens off became a problem. While the Jockey's had a lot of know-how about genetic manipulation, the Aliens' capacity for mutation had overwhelmed the artificial barriers their creators had put in place. Unable to effectively control the factories producing the symbiote, so too did the symbiote become uncooperative with the Jockeys. Too late did the biomechanoids realize the Aliens' meticulously crafted ability to survive via mutation allowed them to affect the symbiote.
All at once the Jockey's realized they had unleashed in their midst a sentient plague.
The Jockey's could not recover; they had created something that was too capable and too efficient to combat.
Millions of years later all humanity knows of the Aliens is that they are too capable and too efficient.
Dangerous killers outside of their hives, inside ... they are virtually omniscient thanks to the nature of their symbiosis with it. Any creature that's not an Alien can be consumed by the hive itself or, perhaps even worse, be affected by the psychic hive mind dominated by the Brood Queen Alien. If someone should be lucky enough to escape the Hive alive, the psychic connection it briefly shared, likely unknowingly, with his or her pursuers diminishes only over distance and time. It is quite possible the Brood Queen and to some degree even the drones, can continue to affect the mind of these unfortunate escapees, driving them mad or subjugating them so they willingly return to sacrifice themselves.