Ralph Karlsson [Unknown]
Ralph has crossed the breach almost more times he can count - there's been at least a hundred timelines he's watched fall (in the opening state, he has yet to save even one). This continuous cycle of warfare has made him ruthlessly efficient, being unwilling to even sleep if he has to, as he feels every second counts... and every second that slips away could be the critical moment lost to the Vek. He's come a long way from the wide-eyed soldier he first was (it seems like several lifetimes ago, and it was), and he tries to avoid attachments to the other pilots, as he knows how likely they are to die in battle. He has never said which island he hails from, and there are suspicions he may have come from somewhere beyond the Corporate archipelago... possibly even from a space station. If true, Ralph has refused to confirm it, although in a few timelines, both Bethany, Harold, and Isaac have commented on the Time Pod's architecture as being modeled off of space-faring tech (notably a launch capsule of a rocket... or an escape pod of a rocket).
Bethany Jones [Pinnacle]
Bethany Jones served as a physics engineer at Pinnacle, helping design and refine Pinnacle shield technology. Having only grown up on Pinnacle, she's somewhat sheltered with regards to the other islands, and she tends to trusting of others, taking them at their word. She loves the cold and the snow, but she's also excited by the opportunities to see other islands in the Corporate archipelago and learn from the people there. While she and Isaac are technically brother and sister, there hasn't been a timeline where they both were alive to realize this (either Bethany dies at a young age, or Isaac dies - only one of them could be saved in the womb b/c of a chronic medical condition their parents had). Bethany has had a more positive upbringing than Isaac, and her genius is tempered more with empathy and optimism than Isaac (who had a much more difficult childhood).
Abe Isamu [R.S.T.]
Sometimes jokingly called "Honest Abe" in previous timelines, nothing could be farther from the truth. Abe served as an "expeditor" (assassin and "black box" work) during the early years of CEO Kern's rise to power, and he took on many names and identities in service to R.S.T. to handle any "difficult issues" that would arise that needed to be dealt with by the corporation. He is ruthless when given an objective (in this case, fighting the Vek), and served as ground support in his original timeline before stealing a Mech from a dying (?) pilot and using its breach technology to escape the timeline after the squad perished in the volcanic island. Since then, "Abe" has followed the orders of his first CEO Kern and is determined to keep fighting until every Vek in every timeline is defeated... a hopeless task, but "Abe" realizes he has little else to fight for, and even if he were to remain in a timeline he saved, he could not deal with the idea that other timelines were still in jeopardy. He has yet to encounter his duplicate, and if so, he may not recognize them due to surgery and the fluctuation of identities his job required before the Vek attack.
Harold Schmidt [Archive]
Harold is as close as they come to an engineering "sociopath" (this is not the clinical term - co-workers in previous timelines used to call him a "technopath," but even that's not an accurate term for his lack of empathy and social skills). He finds humans uncomfortable and confusing, and takes solace in tinkering with robotics and machines who have clear rulesets and reasons for what they do. In his original timeline, he served a brief term at Detritus (where he seemed bored and uncommunicative), then was rejected from Pinnacle due to his psychological exam, then found a home in Archive, studying and doing restoration work on Old Earth robotics. He initially applied to Archive's open-call for pilot training so it could get him closer to the Mech technology, then it was discovered he did well on the pilot exam (better than most Archive volunteers), and he agreed to serve as a soldier as a way of giving him access to the cutting edge of Mech technology. (Note that Harold doesn't bear any ill-will toward Detritus and Pinnacle, nor do they bear him any ill-will... however, both Singh's predecessor and Zenith saw Harold's lack of empathy, and were worried it could lead to accidents or disregard for human life while he was carrying out his duties.)
Prospero [Detritus]
In its original timeline, Prospero was a recycler robot from Detritus. Its job was to monitor region safety in Detritus disposal sites, but was severely damaged in a disposal accident (this was in the days before Vikram was CEO). The "recycled recycler" robot was sold at a discount to Archive as a groundskeeper for some of the nature preserves, and it seemed to take to the work, translating its knowledge of chemistry and recycling technology to help cultivate gardens (and when it wasn't able to do this, it would devour all books on botany, biology, and even spiritual books related to nurturing and growing of all life forms). It would have likely have remained a quiet hulking gardener were it not for the emergence of the Vek. When the Vek erupted on Archive, the robot followed its directives to protect the nature preserves and saw the Vek as nothing more than garden pests to be eliminated to protect the plants. When Archive was able to send reinforcements to the region, they found Prospero still quietly tending its garden, now fertilized with Vek corpses.
Much like Gana, Prospero is viewed with some suspicion due to the robot uprising, but like Gana, Prospero follows orders and has proven itself on many occasions. When traversing to a new timeline, Prospero seems to actively avoid returning to Detritus. The reason for this is unknown.
Lily Reed [Archive]
Lily was an orphan found at sea at the age of seven (she's now 20), then found and raised by Archive when her makeshift life raft came in sight of their island. Lily was only newly-employed at Archive before she answered the open call for pilot training - some employees may have frowned at her sudden shift in career were it not for the urgency to find soldiers to fight the Vek. Unlike others at Archive who wished to slowly tinker with the Mechs, she embraced her training whole-heartedly, soon learning to use the Mech with one of the fastest training times of any Archive pilot on record. Lily's gone through only a few timelines (or maybe just one) and even seeing the end of the world hasn't dulled her enthusiasm for stopping the Vek. She is a talented pilot and engineer, and her near-hyperactive energy has found a good outlet on the battlefield.
Chen Rong[Detritus]
Chen is Henry Kwan's opposite. He's dutiful, conscientious, and puts other's safety before his own. Chen was a high-level manager of one of the key Teleportation Waste Sites in Detritus (much like a central hub to distribute waste to the proper sections of the island), and was responsible for transporting and managing hundreds of disposal lines at once (much like an air traffic controller in the old days, but this was governing the movement of waste, junk, and insuring there were no back-ups or stoppages in the supply line). It is believed this gave him considerable skill in tactics that was recognized during the open call for pilots when the Vek first attacked. Unlike Kwan, Rong didn't volunteer because he wanted to fight, or rise above his position, he did it because he believed it was his responsibility. Since then, he has proven a capable and reliable solider, although he lacks Kwan's battle instincts.
Henry Kwan [Detritus]
Henry Kwan is perhaps the least reliable and least safety-minded worker in Detritus. It seemed he would be forever regulated to a low-level A.C.I.D. report-filing bureau at Detritus - until the Vek attacked. Impulsively, he applied for the open call for pilot training, and he passed the aptitude test with flying colors (his instincts and reflexes seemed to shine in "think-fast" situations - as well as situations where he could cause a lot of damage... intentionally.). While hardly the most modest employee at Detritus, his accomplishments in battle have only fed his ego. Despite the timelines lost, Henry seems to see it all as some sort of game, and remains distant from the actual suffering - some suspect his jokes and boasting are a psychological shield, and thus, are afraid to pierce it, in case he loses what gives him his fighting confidence in the first place by dwelling on his failures vs. his accomplishments.
Camila Vera [R.S.T.]
Camila is the sixth adopted daughter of Jessica Kern (who maintains an extended family of 20, none of them related by blood) from her Origin Timeline. She is a ex-cartographer and meteorological scout from R.S.T. - she was previously assigned to do field surveys and do "terrain testing" in areas where the corporation were testing out new terraforming weapons (she was essentially terraforming "Q.A."). In this role, she became an excellent pilot (the others are dead, it's an unforgiving job) and developed a "sixth sense" for piloting craft in hazardous conditions and trusting her instincts to "move" whenever she sensed a quake or collapse in the ground was about to occur. She has since channeled this sixth sense into combat, learning to anticipate and evade Vek webs as well as knowing how to pilot her Mech in the thickest dust storms without handicapping her combat efficiency. She was one of the first volunteers to fight the Vek in her original timeline after the death of her adopted mother, and also (she's never revealed this to anyone else) she has always had a loathing for insects, so she takes satisfaction in wiping out the giant varieties (the Vek).
Gana[Archive]
Gana is a construction robot adapted for combat by uploading a mix of old and modern combat routines from the Archive libraries (think Baymax in Big Hero 6). This has had partial success, and what happened to Gana is evidence as to why he was the only construction robot so outfitted: while an excellent soldier, his expressions and outlook are a blend of construction-focused speech mixed with ruthless pragmatism. As an example, Gana may categorize an otherwise simple repair as "offending parts have been executed" - or he may start ordering a building's infrastructure to "hold the line" to prevent a collapse. Soldiers who have served with Gana for an extended period of time have come to ignore its unusual speech patterns as the robot is incredibly effective on the field (and obeys orders), but Gana can be disconcerting for new pilots. Gana has indicated that when the war with the Vek is over, he would prefer to return to his construction duties, and finds he experiences "reduced job satisfaction" in fighting the Vek.
Note that given the recent rise in prejudice against the Pinnacle robots, Gana has suffered similar discrimination and several officers have questioned if Gana's "sanity" in case he may malfunction like the Pinnacle robots.
Isaac [Pinnacle]
Isaac has seen too many timelines collapse, and seen too many permutations for how things can go wrong - his high intelligence actually works against him, rather than makes him more confident because he can imagine all the ways things can go wrong (think Chidi Anagonye in The Good Place). He feels ill-suited for being a soldier (his squad mates usually agree, but his scientific knowledge is indispensable).
While he and Bethany are technically brother and sister, there hasn't been a timeline where they both were alive to realize this (either Bethany dies at a young age, or Isaac dies - only one of them could be saved in the womb b/c of a chronic medical condition their parents had). He respects machines and sees them as equals due to being raised on Pinnacle (he has faith in Zenith, perhaps too much as he feels she's too intelligent to do anything wrong).
Isaac is as much of a genius as his sister, although self-doubt weakens him. He has considerable knowledge of aeronautics, physics, gravitation theory and manipulation, and a number of other fields. It is likely Isaac could master any science he chose to, his only block is his own perceived limitations.
Silica [R.S.T.]
Silica is a hybrid of Pinnacle and R.S.T. technology, believed to be one of the first (and possibly only) artificial intelligences devoted to terrain architecture.
In "his" original timeline, Silica was responsible for first detecting and studying the Vek, and eventually was modified to investigate their hives... this nearly ended catastrophically, and Silica was recovered and his programming altered from terraforming to terraforming-based-combat... the concept of using the existing terrain and shaping it, exploiting it, and using the surrounding region as a weapon against the Vek.
When Silica jumped timelines, his original programming was unknown to every subsequent timeline, and they have seen him only in his role as a environmental tactician, designed to help the islands defeat the Vek.
Archimedes [Pinnacle]
Archimedes is a cutting-edge robotic intelligence (a Sentient, he finds the term "robot" and "artificial" to be discriminatory) from Pinnacle designed to act as a Human Relations officer. It has come from a timeline where Pinnacle "oversaw" the islands (the Pinnacle Island Network: P.I.N.) and tended to the humans' needs (much like how you would take care of animals on a farm, but not in a mean or ruthless way the Sentients simply saw themselves as benevolent caretakers to keep the humans from hurting themselves).
Zenith has refused to allow Archimedes access to her network, for fear that his directives may corrupt programming on Pinnacle (if this occurred it would be inadvertent, but it is a possibility). Archimedes believes the rioting behavior of the robots on Pinnacle is due to either (1) a contradictory directive they are attempting to follow or reconcile, or (2) the possibility that the arrival of sentient pilot variants from other timelines may indeed be interfering with the natural programmatic order on the island.