The protagonist of Season 1; Boone is initially offered a position with the companions, turns it down because he and his wife are happy where they are, and is understandably suspicious when his wife is murdered shortly thereafter. He accepts a job as one of Da'an's Companion Protectors, while working with the resistance, to get to the bottom of his wife's death.
Anti-Climax: When Boone asks Da'an if Da'an is responsible for his wife's death, Da'an denies it. For various reasons, Da'an can't be lying, suggesting there is some sort of high-level conspiracy. It turns out Sandoval arranged it to get Boone working for them, and that's it. Presumably, he didn't think it worth Da'an's time to mention it.
However, in the pilot of season 2, Zo'or berates Da'an for hiding from him that he had Boone's wife killed, and Da'an does not deny it.
The Bus Came Back: To the surprise of anyone still watching during the fifth season; the end of Season 1 leaves no indication that Boone survived, only for him to be brought back four years later.
Heroic RROD: Overuses his skrill to the point of passing out in order to take out what appeared to be Taelon weapon, actually the first Jaridian probe, gone awry on a small town.
Killed Off for Real: Comes back in Season 5 only to be killed off-screen in the penultimate episode.
Put on a Bus: Is altered by Sandoval to be capable of reproducing with the Jaridians and promptly sent off to them. She's married to a Jaridian and has a child the next time we see her.
The protagonist from Season 2 until Season 5, Liam's father is the last survivor from a race the Taelons previously exterminated.
The Chosen One: His unusual genetic makeup is an important part of the solution to the Taelons' Core Energy problem.
Commuting on a Bus: Liam is never entirely sidelined, but Season 4 puts increasing amounts of effort into building René up as the new protagonist.
Hand Blast: Being part-Kimera, his palms have the Shaqarava organ, which allows him, when the plot demands it to emit energy from it.
Heroic BSOD: Has one of these early on when a time-travel incident convinces him he's going to go insane and gun down the resistance. The problem turns out to be something, and someone, else entirely.
Refuge in Audacity: Liam spends some time trying to convince the rest of the resistance, particularly Doors, that they can trust Da'an, and is constantly rebuked. His solution is to bring Da'an to their base of operations unannounced, and let the fact that Da'an does not turn them in to the authorities speak for itself. Years later, this backfires spectacularly.
Properly Paranoid: Even other resistance members think Doors is a little unhinged at times, but he's usually not wrong to be worried about something. It can be said that this applies to his starting the resistance as well, as there is little indication that anyone else initially distrusted the Taelons.
Taking the Bullet: In the pilot, he sees a Laser Sight on Da'an and blocks the bullet of the sniper. Of course, this is all a part of him trying to fake his death and go underground. Later, we find out that a bullet can't really hurt a Taelon anyway.
Son of Jonathan Doors, the two are estranged.
Cycle of Revenge: In retaliation for the below shenanigans, he keeps playing nice with the Taelons, gets his hands on a metric crap-ton of Core Energy for a science experiment, and promptly dumps it into space. Liam and René are aghast that he doesn't realize the Taelons will undoubtedly kill him in retaliation; he admits he guessed as much and just doesn't care.
Heel-Face Revolving Door: Starts out hating his father but being no friend to the Taelons. In Season 2, he helps his father run for President, then turns on him at the last minute, getting the Taelon-friendly candidate elected in a landslide. Comes to a head when he later kills his father, but it turns out to be a...
Mind-Control Device: The Taelon computer in the office building Jonathan works at had been subtly brainwashing him for years. Once its influence is removed, his behavior radically changes.
The resistance's technical expert.
Good Guy Bar: Owns the Flat Planet Cafe, often used as a resistance hub.
Non-Idle Rich: Has a lot more money than the bar would give him; when Doors retires the resistance's underground base, Auger decides he wants it to live in and trades a set of rare paintings for it.
Put on a Bus: Eventually decided to get the hell out of dodge and was replaced by Street; still made a handful of appearances afterward, but didn't come back for good.
The Smart Guy: Is almost always the one to come up with solutions for technical problems, although he sometimes bites off more than he can chew and causes them.
René started as an executive in Doors International and quickly took an active role in the resistance. She ends up as the protagonist of Season 5.
Ace Pilot: Seems to be as good as Lili by Season 5.
The Chosen One: Ra'jel and then Liam tell her it's her destiny to end the alien-involved conflicts on Earth. In the end, they convince her to take the Taelon mothership and use it to begin humanity's journey of exploring space.
Strawman Has a Point: She becomes extremely distrustful of alien life as a concept. Ra'jel calls her out on this and René answers, correctly, that every alien government or force yet encountered by humans has had malevolent intent, barring a few dissenting individuals. Ra'jel still convinces her that she shouldn't shy away from further first contact with other life.
Auger's replacement and a math whiz.
The Chosen One: More literal than René; her genes give her the ability to work with the extremely complex math needed to solve the Taelons' Core Energy problem. It's hinted that Ma'el's modifications to the human species ensured someone like this would eventually be born.
Taelons and Associates
A race of Sufficiently AdvancedEnergy Beings who come to Earth with the promise of peace. As the series goes on, it becomes increasingly clear that they aren't as advanced as they like to think and that their promises are made to be broken.
Abusive Precursors: Technically, only one Taelon was a precursor and he told the others to stay away from Earth. To say they didn't listen would be an understatement.
Energy Beings: Deconstructed; the Taelons didn't evolve naturally into their current form, and they can't actually replenish the energy they're made of. Their visit to Earth comes at the twilight of their species, as, without intervention, they'll soon all be dead from lack of energy to burn.
The North American Companion and a dissenting voice for the Taelons' generally malevolent policies towards other species.
We Used to Be Friends: Da'an sells out several resistance cells to take suspicion off of himself once he feels like Zo'or is close to either exposing him or faking evidence to expose him. Liam never forgives him for it. This has the side-effect of further reinforcing Jonathan Doors' Properly Paranoid tendencies in hindsight, but Doors is long gone so it isn't brought up.
Core Energy Is Thicker Than Water: Da'an lets a lot slide when it comes to Zo'or, his child. When he learns that Zo'or is responsible for General T'than's death, not only does Da'an keep Zo'or's secret, he gives Zo'or some of his own Core Energy. Contrast with Zo'or, who is perfectly willing to throw Da'an to the wolves if it suits him.
Nice Job Breaking It, Hero: The Taelons can test one another if an accusation is made that one has cannibalized another for their Core Energy, an act that carries the same repugnance as "normal" cannibalism does to humans. Da'an eventually decides that Zo'or has to be deposed regardless of their family ties, but by then, too much time has passed for the test to work.
Who Wants to Live Forever?: A failed attempt to join with a Jaridian kills the Jaridian and leaves Da'an with enough Core Energy to last a thousand years. Da'an's reaction is this, because the Jaridian was a friend and because the prospect of outliving the rest of his species horrifies him. Eventually, he shares his surplus of Core Energy with the remaining Taelons.
The last Taelon born, and Da'an's child, Zo'or becomes leader of the Taelon Synod in Season 2. While the Taelons clearly had an agenda that didn't necessarily include humanity's best interests before, Zo'or's leadership begins a downward spiral that doesn't end until Season 5.Like Sandoval, Zo'or appears in all five seasons, but has only a small roll in Season 1 and a single episode in Season 5.
Big Bad: For Seasons 2 through 4. Arguably for Season 1; he only makes a handful of appearances but his scheming began off-screen long before he became a regular.
Dropped a Bridge on Him: Seemingly happens in the Season 4 finale; is brought back for an episode in Season 5, and is killed off-screen shortly after the episode fades out.
Greed: Zo'or eventually develops a sense of greed for straight-up wealth after dealing with humans involved in political and economic power-play for years. His need is so bad that he starts hoarding gold on the mothership, and hallucinates that it's been stolen when he checks on it.
The only character to appear in all five seasons as a regular, formally an FBI agent before going to work for the Taelons.
Brought Down to Normal: In an episode of Season 4, Sandoval's CVI breaks down and must be removed; Zo'or teases that this means he'll have to give up his Skrill and use a lowly energy pistol. It turns out later that the entire thing is a ploy in case the situation he's walking into is a trap so he can hide his Skrill and then use it to escape after his pistol is confiscated. In Season 5, this happens for real after the the nuclear strike against the Taelon mothership severely injures Sandoval and kills his Skrill.
Genre Savvy: When Sandoval's wife calls him out of the blue three years after her apparent death, he immediately suspects a Jaridian trick, as Jaridian probes can masquerade as a human. It turns out it really is his wife, which is something the viewer knows. What neither he nor the viewer knows is that she's come out of hiding to pull a con job on him.
Hidden in Plain Sight: Lampshades this when he discovers the Lair in the series finale, lamenting that he's been looking for it for five years since it was the base of operations for Doors' resistance, and has literally walked right over it several times.
Heel-Face Turn: Teased early on when we see he despises the Taelons for what they've done to his life when their control is briefly removed. Once it's removed permanently, however, Sandoval turns into a scheming manipulator, and his chance at a real Heel-Face Turn is ruined by his own greed.
Dropped a Bridge on Him: Howlyn's lack of patience when he finds his starship causes it to be forever grounded and inspires his newly-awakened second-in-command to kill him. None of the heroes are even present.