System: Luyten's Star
Planet: Luyten II
Since we already have plenty of machine-based races (Jeff, Drenkend, the AI for the Trandals), I think we should have a biological race that can absorb whatever they scavenge into their DNA (sort of like the Umgah, who could change their DNA themselves; rewrite it to fit each situation)
Evolution: The Sik-Mu-Thieln evolved on a highly competitive planet, filled with flora and fauna all desperate and ferociously competing for the same resources. Their natural bodies (or Core, as they refer to them) are slender and soft-skinned - slimy almost, with a rigid backbone, but floppy appendiges braced from the inside by only cartilage. These appendiges would regularly be pulled off during any struggle or fight... in a very painful way. Overall, they were very weak, but their slippery skin and easily-torn-off appendiges helped them escape more often than not. This, coupled with their intense group mentality and the need to rely on other members of their species for both physical and moral support offered them better chances at survival and helped them establish the first tribes and safe places on the planet. Banded together, they would ultimately become the rulers of this world. But it wouldn't come quickly, or particularly easily.
Their real leg-up on their ultra-competitive planet was the ability to scavenge after each conflict... not for tools - the twist is that they would use pieces of their fallen foes. The physical aspects of other species that performed better than the Sik-Mu-Thielen would be removed (read:torn off) from the bodies of the fallen, and incorporated into the genetic structure of their own bodies, replacing limbs, mandibles, muscle and eventually organs, while adapting them to their own bodies. You name it, there was nothing about the Core that started out AS good as other species had developed (a lot the same way Humans aren't technically the best on this world, at almost anything when compared to animal counterparts.) They weren't the fastest, they weren't the most agile, they weren't incredibly strong, they didn't have as good a sense of smell as the packs of roving beasts, the regenerative power of plants, various types of locomotion, etc. It all had to be taken from creatures that had developed in better ways. This incorporation of foreign bodies built the basis for their entire culture.
Over time (and a lot of trial and error), everything became about achieving perfection of form - if a competing species was better at tearing food with their teeth, then they would exterminate the Chigriss, and once the battlefield lay quiet, subsequently scavenge their teeth. If the legs on an Aandvis provided better locomotion, they would be forcibly removed and reappropriated to the Core. If the Urrdvink had developed incredible eyesight, they were farmed for their eyes and brought into the folds of Core DNA. Each appropration of some form, making them stronger and more powerful. Photosynthesis, locomotion, extreme digestion of otherwise inedible material, camouflage, sonar, breathing in water or air, flight, brute strength - and little by litter, they grew in adaptability as they absorbed more and more traits, to the best their planet's evolution could provide.
Their current incarnation is a twisted, grotesque, terrifying beast (Which I think is something SCO doesn't quite have right now - a truly horrifying alien), that shows off the different aspects of the lifeforms they've added to their own - they're vaguely snake-like in shape, with millions of tiny cilia providing extreme locomotion, covered in limbs with amphibian-like gripping capabilities, hulking wings, a hard-carapace exoskeleton for protection, a mouth with row after row of razor-sharp teeth, big central eyes with multiple smaller eyes to give them an advantage at other angles, and giant ears they've stripped to provide sonar and excellent hearing capabilities. They've got gills for underwater breathing and rows of smell-receptors lining their skull. It's not pretty, but that's not what they're concerned about, is it?
Here's just a rudimentary concept:
The concept art needs a lot of work and development to really nail their current incarnation, based on clever commentary from DarkGildon: "I think they shouldn't look like anything we would imagine a creature to look like. I think it would make more sense for them to become beings of practicality. So the idea of having a lot of eyes makes sense, but I don't think they would be placed there, and maybe they'd be some new form of eyes. Shit that grows out of their body and looks like alien receptors. They would probably have them all over the place, so they get 360 degree sight at all times. They'd still be ugly as sin, but it would be because they no longer resemble anything that should exist." It's true, their bodies should be governed 100% by practicality.
Soon though, the planet had been completely stripped bare and all competition eliminated - there could be no more upgrades from the current pool. But, they couldn't stop there. They hungered for more improvement. Their mission had just begun. So, they built a fledgling and inexperienced space fleet and set out to harvest better parts to improve the Core further. Without the need or desire to stay on a planet that provided them with NO further improvement, they constructed a hulking Ark that their race lives on - and each new system they visit, they harvest the lifeforms there, in search of their next biological upgrade.
Their fleet construction and strategy was heavily influenced by their biological counterparts. While their ships aren't outstanding on their own, they are always, constantly, on the hunt to harvest others' tech and use them as their own. When an opponent's ship goes down, if their weapon is deemed superior, it is scavenged and attached to the Sik-Mu-Thielen ship. If their propulsion method provides bonuses, it's welded into place and incorporated into the systems. Any other perks - cloaking, point-defense, AMI, whatever - it can all be scavenged and adapted to their ships. This plays out within the systems of super melee:
Primary Weapon: Short-range plasma-cutter - this relatively short-range and low-damage weapon employs multiple small plasma cutters that seek out experimental new weapons-or-defense tech on the opposing ship and attempt to slice it off. This employs a temporary negative buff to the enemy ship that shuts down the weapon or tech for a couple seconds. It should be random, so sometimes it will disable their engines and they can't thrust for a while, another time one of their weapons stops working. Also could have a chance to cut a hole in the ship, that bleeds a spray of crew limbs, organs, and viscera into the void. So, when a ship is hit, particles of bio or mechanical matter start floating around the space, that can then be picked up with...
Secondary Weapon (improved by clever feedback from EmperorZA and Bleybourne): Tractor Beam Scavenge. This is a harvesting tractor beam that pulls in said-particles and adapts them to the owner's ship - effectively replacing the primary (or secondary) weapon with a version of the enemy's weapon for a given time, or replenishes some disabled crew with new body parts. The weapon effect wears off after awhile, given that the method isn't perfect at integrating the alien tech, allowing them to use the plasma cutter again on a new ship the next round. The two abilities (cutter/tractor) can also be used in the asteroid belt to extract and pull in metals to rebuild damaged systems or recharge batteries. Same goes for the wrecked hulks of expired enemy ships.
And so they march on, in search of the perfect form...
As for interaction with the player, TheQCraft nailed it below - I got chills reading what he wrote. I can see the conversation screen now. Everything seems to be going so well, they're friendly and open to dialogue - but only because they're feeling you out, the humans' strengths and weaknesses, making a MENTAL CATALOG of parts of you they'd like to incorporate into themselves!!
You have a great conversation, you've reached an understanding based on your adept navigation of diplomacy - BUT THEN THEY SAY...
"Well, you've convinced me. And by convincing us, we realized we lack one thing... In order to deftly navigate the politics of the universe, we have decided that we really need a *TONGUE* that is so very capable of formulating speech in such an eloquent way... PLEASE HAND IT OVER." *COMBAT* Hah!!!
Or what if... they meet you and don't necessarily see *ANYTHING* about humans, that they like. We're pretty unremarkable, in general. These beings are not "evil" in any way. Their primary driving force is improving their own biology. If they encounter an alien that's of no use, there's no reason for them to be aggressive at all. They could instead be manipulative, using us humans as a means to get closer to other aliens who.... might be more beneficial to them than our weak limbs and terrible eyesight. So they could meet us humans, but we'd basically be incredibly useless to them. But maybe one of the alien races we're allied with aren't... and so they offer a very happy, helping hand and we have the choice to welcome them as allies.
If the player agrees? Everything is great! For awhile...
But then, one day, one of your friends' influence bubbles just disappears on the starmap (HINT: Hunam's Ellerians are a good prospect lol). No word, no distress call, nothing. Kind of like the ZoqFotPik, if you didn't defend them. Their bubble just collapses. Gone. The player must then fly to their homeworld, and there's no one but Sik-Mu-Thieln scavengers.... and the dessiccated, vivisected remains of our once-friends. That's a great choice for the player to have! If you ally with them, you don't know this going in, but at some point in the future, some friendly race disappears completely, and you lose an ally. But what happens next?
Well, to the Sik-Mu-Thieln, this doesn't necessarily mean all-out war. They have their new components they have integrated. They're happy to stay friends! Besides, now they have bigger fish to fry: The Scryve.............
So NOW you have the most important decision of all:
Destroy them and lose ANOTHER ally?
Or keep them on your side, and salvage the remains of what's left of your alliance.