How much has Amazon Prime after being evicted from its original home on the Syfy network. Boasting a ionate fan base that was instrumental in The Expanse's season 4 salvage, much of the show's popularity comes from a fascinating premise and a compelling core mystery, all set within a believable (relatively speaking) science fiction universe.
And at the very center of that mystery is the Protomolecule. Since its introduction in The Expanse's opening scene, virtually the entire story has orbited around this mysterious blue goo and the questions it poses. Tensions between Earth, Mars and the Belt might have been ready to explode at the drop of a feather, but it was the Protomolecule that provided the fateful spark, and the material has only become more invaluable and more deadly to the Sol system ever since.
As the saying goes, close one door and another one opens, and learning about the Protomolecule over the course of The Expanse has built towards the secondary mystery of the Protmolecule's creators. Who were they? What did they want? Who wiped them out? These questions have been expanded upon, albeit not completely, in Corey's novels, but the following will focus mainly on what is known from the live-action TV adaptation of The Expanse. Here's everything we know about the Protomolecule and the Ring Builders up to and including The Expanse season 4.
What Is The Protomolecule?
The story of the Protomolecule begins several billion years prior to the start of The Expanse in a distant part of the galaxy. A powerful ancient civilization (more on these folks later) designed and made the Protomolecule via some unknown method of fusing incredibly advanced biological and technological science. Despite being synthetic in origin, the Protomolecule bears the hallmarks of a sentient being and is programmed with several primary functions. The chief goal of the Protomolecule is to construct ring gates that connect disparate and faraway solar systems, allowing for rapid travel and conquest across the galaxy. In order to achieve this, the Protomolecule seeks to learn via deconstruction and infects whatever it comes into with, whether that be a human, a spaceship or an entire asteroid. After merging with human hosts, the Protomolecule is able to take on some of their characteristics, appearing to Holden in the avatar of Miller. The Protomolecule appears to communicate with itself and others via some kind of hive-mind network.
As well as connecting the galaxy, the Protomolecule's final ring gate form is also designed to function as a weapon against all who might threaten the Protomolecule or its creators. Were it not for Jim Holden's intervention, this grim fate would've befallen the Sol system in The Expanse season 3. Despite an inherent drive to create ring gates, it does seem that the Protomolecule was intended to be a flexible asset. In The Expanse season 4, Ilus is crawling with Protomolecule-infused structures that turned the entire planet into a massive power plant for the Ring Builder civilization. This suggests that as well as creating rings gates and destroying enemies, the Protomolecule can essentially be used for a multitude of terraforming purposes, taking orders from its creators and adapting to new situations. In rudimentary , the Protomolecule could be described as an all-purpose real life hacking code that rewrites whatever it touches to suits its own ends.
Much of the Protomolecule usage seen in The Expanse is a product of Earth and Mars bastardizing the ancient technology for power or profit - the Protomolecule hybrids seen in previous seasons, for example. These supersoldiers almost certainly weren't part of the Protomolecule's original function, since mastery of such omnipotent technology negates the need for angry glowing foot soldiers. No one currently alive in The Expanse fully understands the Protomolecule's inner workings, but the likes of Jules-Pierre Mao and Elvi Okoye have tried their best.
Who Were The Ring Builders?
Speaking of the Protomolecule creators, even less is known about this mysterious race than the Protomolecule itself. The impossibly advanced science behind the Protomolecule and the structures seen on Ilus in The Expanse season 4 prove that this unnamed civilization were highly advanced. Thanks to Holden's conversations with The Investigator, we also know that the Ring Builders formed an empire throughout the galaxy using their Protomolecule technology, and just like the strange blue substance they crafted, it's difficult to know where this civilization's moral com pointed. On one hand, The Investigator gives the impression that the Ring Builder empire was peaceful until they came under attack, but one look at Ilus proves that the race were willing to retrofit entire planets for their own ends, regardless of what might've been present where then arrived. The Protomolecule also destroyed entire worlds while trying to kill its enemies, which almost certainly left a colossal death toll behind in collateral damage.
The first instance of Protomolecule in the Sol system came via Phoebe, a lump of rock that would ultimately become a moon of Saturn. It's likely that Phoebe arrived as part of the Ring Builders' expansion in eons past, where samples of Protomolecule were aimed towards habitable solar systems with the purpose of forming a ring gate there.
How the Ring Builders controlled the Protomolecule is still unknown, but the connection between Protomolecule.
What Happened To The Ring Builders' Civilization?
After many thousands of years as the dominant force within the galaxy, the ring builders entered into a war with another unknown alien race - a conflict they ultimately lost. The Investigator reveals that despite boasting the power of the Protomolecule, the entire civilization is no more, and now the remaining Protomolecule wishes to find out why its master race was destroyed and what happened to those doing the destroying. The only clue The Expanse gives about these aggressors is the bomb at the end of season 4. Deep within Ilus lies a weapon left over from the aforementioned ancient war, and the device is capable of destroying every ounce of Protomolecule within a given radius. Weapons of this ilk are likely how the Ring Builders were defeated in the first place.
The Expanse has yet to confirm whether the Ring Builders' killers were ruthless invaders determined to take down an established civilization or a rebel uprising fighting back against the rule of an intergalactic government backed up by a powerful blue servant. The Expanse suggests that the creation of the gates might have invited enemies onto the Ring Builders' doorstep. Viewers also don't even know if these genocidal aliens are still alive somewhere out in the vast reaches of space, or whether they met the same end as the Protomolecule's creators. The bomb on Ilus harmed the Protomolecule without touching organic beings such as Elvi Okoye, who managed to right through the sphere unscathed. However, Elvi did describe feeling a "presence" when she came into with the alien bomb and Holden claims to have experienced something similar when ing through the ring gate, hinting that the awakening of the Sol ring gate might've caught the attention of whoever wiped out the Ring Builders in the past.