History Characters / TheExpanseTVExtrasolar

* AIIsACrapshoot: Perhaps because of ''extreme'' incompatibility with human biology, the Protomolecule found on Phoebe can at times act... glitchy.
* TheCorruption: While the Protomolecule isn't actually malicious, it will relentlessly follow its directive to consume and repurpose any biological matter it encounters. This process often leaves said matter (e.g. humans) as little more than a mindless husk.
* CosmicHorrorStory: After making contact with the Ring-builder database at the end of Season 3, Holden comes to the realization that the Protomolecule isn't trying to destroy humanity -- it just doesn't ''care'', one way or the other. It's just terraforming technology created by an incomprehensibly advanced and long-dead alien civilization, whose secondary purpose is to build Ring-gates to connect new star systems with wormholes. As Holden put it, the Protomolecule's purpose is to build "roads" and it doesn't think about us any more than we care about destroying anthills when we pave a new road.

* ImportedAlienPhlebotinum: The Protomolecule came from an extrasolar object cast stuck in orbit around Saturn.
* LostTechnology: The Protomolecule left behind on Phoebe was the only ''active'' bit of Builder technology lying around. Everything else was long dead or inert, at least until Holden and The Investigator started pushing buttons...
* MadeOfIndestructium: ''Nearly.'' The stuff is ''notoriously'' difficult to destroy. Not only does it survive an asteroid impact on [[DeathWorld Venus]], it outright rewrites the laws of physics and begins building the Ring inside the crater. The hellish heat, pressure, and acidity mean nothing to it once it has established itself. Though it ''can'' be destroyed, this is usually only in cases where it hasn't had a chance to perpetuate itself. Small Protomolecule samples and the hybrids can be incinerated by extreme heat, and it's a safe bet that dumping an asteroid full of it into Sol would have worked. Once the Protomolecule has grown to the point it can start forming structures, nothing within the realm of man has the power to get rid of it.

* SentientPhlebotinum: Humans keep attempting to use the Protomolecule to achieve their own ends (ranging from science project to SuperSerum to SyntheticPlague), but the Protomolecule very much has a will of its own and will pursue its goals relentlessly, regardless of how it is repurposed, modified, or shackled.

* WellIntentionedExtremist: From a Builders' perspective anyway. It's programmed to terraform and build Ring Gates and not much more, all other lifeforms be damned. If the Protomolecule ends up being deadly to them, well, they're shit out of luck. This is not so much malice as it is unexpected encounters; the Builders likely never had to contend with other sapient life when colonizing.

The Hybrids ''were'' children who were experimented on by Protogen with the Protomolecule to create near indestructible super-soldiers to sell to the highest bidder. Despite the project being ''mostly'' a success by those parameters, the Hybrids were still directly communicating with the Ring that was being built on Venus.

* BrainwashedAndCrazy: Two-fold. Hybrids are loyal to whoever made them and purchased them, but to also the Protomolecule itself. Gone entirely is the innocent child it once was.

* MadeOfIndestructium: Terrifyingly hard to kill. Holden and his crew were only able to destroy one in the ''Roci's'' drive plume because their weapons simply couldn't harm it. Bobbie was able to kill a recently-made Hybrid by completely blowing away its brain stem with her arm-mounted gatling gun, and she only got that chance because it got distracted by the Ring Gate's completion on Venus.

* PoweredByAForsakenChild: The ''only'' way to create a Hybrid is to expose a child with a rare genetic disorder to the Protomolecule. Their compromised immunosuppressive response allows the Protomolecule to assimilate more easily and without damaging the host.
* TragicMonster: It doesn't get more tragic than this. At one point, they were all children crippled by a genetic disease. Now, they are nothing more than super-zombies controlled by Mao and the Protomolecule.

* AbsoluteXenophobe: The "technology" left behind by the aggressors is downright deadly to anything and everything connected to the Builders. A human who touches the Void Bullet briefly loses consciousness, yet Protomolecule technology that comes into contact with it renders ''all'' networked technology instantly inert and dead. For all intents and purposes, the hostile force hounded the Builders like a plague until it ultimately wiped them out.

* CripplingOverspecialization: Their Void Bullet is fatal to the Builders and Protomolecule technology in general, but humans can pass through it and just see visions of the beings that sent it.

An extremely advanced, ancient, and very much extinct alien civilization responsible for creating the Protomolecule and building the Ring Gates. Several eons ago, they aimed Phoebe -- filled to the brim with Protomolecule -- at Earth in the hopes of expanding their galactic empire, but it was inadvertently caught in Saturn's gravitational field and became one of its many moons. Some time later, the Ring Builders themselves would come face to face with a hostile force hell-bent in wiping them out. The Builders began sealing off the Rings and destroying whole solar systems to "cauterize the infection". Despite the complete shut-down of the Rings, they were ultimately wiped out in the end.

* AdvancedAncientAcropolis: This is what Ilus is, one of the products of Protomolecule terraforming. In fact, most of the planet is ''hollow'', with the inside being what looks to be an enormous temple or facility. [[MindScrew Or ship.]]

* MonsterProgenitor: They created the Protomolecule, which would cause ''irreparable'' damage to humanity. Subverted somewhat though in that the Builders never intended for anything like that to happen -- the Protomolecule is merely terraforming technology that's incompatible with human biology.

* TragicMonster: It doesn't get more tragic than this. At one point, they were all children crippled by a genetic disease. Now, they were nothing more than super-zombies controlled by Mao and the Protomolecule.

* OneManArmy: Their entire appeal to governments is that just one experimental Hybrid can easily take down two platoons consisting of highly skilled marines. Just a handful perfected Hybrids can lay waste to an entire planet.