Deimos

It's quite easy to say that there isn't much to Deimos personality or that he's simply a quiet person willing to do Cain's bidding. But what Deimos doesn't say, he shows with his actions and body language. He's observant, loyal to a fault, and a bit obsessive.

Let's get the biggest characteristic of Deimos personality out of the way and that is his quietness. It's hard to say exactly why Deimos is quiet. He's capable of speaking and when he does speak, he's straight to the point or extremely insightful to the conversation he just has a preference for using his body language is all. Even from the very first introduction of Deimos, it's made clear that he prefers to use his body language when he gives Praxis a knowing look for trying to talk to Abel (no one is allowed to interact with Cain's navigator), or how easily he threatens another fighter with his butterfly knife to show he isn't interested in a hookup.

Cain once claimed that Deimos isn't good at talking and it's pretty clear that Deimos does have a hard time talking when he does engage in conversation; often visibly struggling to speak by nervously fidgeting, swallowing, or clinging closer so he doesn't have to raise his voice above a whisper. Possibly the best example of this is when he reports to Cain that Praxis was talking to Abel, Deimos nodded his head until he was pressed for an answer from Cain. He gives a verbal answer rasping out "I saw them speaking together." But he doesn't speak without looking embarrassed beforehand or clinging onto Cain.

Speaking of clinging onto Cain, Deimos is not shy about his obsession with Cain. He's often seen clinging or grabbing onto the other, much to Cain's displeasure. Heck, he's even thinking about their partnership while he watches two other fighters get it on in the shower and his feelings for Cain. Right before breaking off their partnership, Deimos even tried to forcefully kiss Cain to assert his feelings, claiming that it was only right for them to be together because they were both fighters and from the colonies. Previously, rejection from Cain was just something Deimos deals with until he realized that Cain has feelings for Abel. Then the obsession turned into jealousy.

It's with jealousy that Deimos exhibits that ultimately betrays Cain by revealing Project Thebes to Abel thus ruining the romance between the two. But he doesn't do it out of malicious intent like his navigator does as Deimos does try to offer Abel some small comforts. (Telling his navigator to knock it off when Abel starts to cry from the news and trying to offer Abel some kind words about how Cain wasn't worth it.) Prior to the changed feelings though, Deimos was extremely loyal to Cain.

He is loyal to a fault to Cain, willing to do Cain's dirty work and willing to be the object of Cain's anger. In his first scene with Cain, we see that in the way that Deimos immediately reports to Cain after warning Praxis off from Abel with a look. He's been told to keep tabs on Cain from all angles of Cain's life whether it be from Abel, their commanders, or other fighters. When he told Cain of Praxis "talking to Abel" we see a brief flash of fear in Deimos eyes between the two fighters (perhaps it's how close he's clinging or that he knows Cain's anger and brashness) before being thrown to the ground. In this moment, Deimos flinches and fully expects Cain to kick him while he's down and he actually looks a little dejected when Cain leaves him alone to deal with Praxis. This could be their power dynamic in that Cain had repeatedly told Deimos to knock off his clingy tendencies or it could just be Deimos loyalty. Perhaps it was just Deimos being a pushover because it's implied with his relationship to Cain and the rocky relationship with his own navigator that he let's others decide for him what to do. (Cain speaks for him while his own navigator tried to force him to stop eating at the navigators table with Cain, Abel, and Ethos in the same scene.)

Deimos is also observant. As stated in the history section, Deimos was the one to notice that Cain's feelings for Abel were romantic ones. A large part of his observation skills probably deal with his gift for stealth and his preference for communication via body language. But he is diligent in his observations, noticing when Praxis tried to talk to Abel or when Abel obviously couldn't handle any more scolding from Phobos after the truth about Project Thebes came out. In the video game, Starfighter: Eclipse, Deimos also noticed that Abel's behavior was odd and tried to stop his evil plans from being realized. Thanks to his diligence and care for Cain, he and Helios were able to stop Abel if you pursue the Deimos story route.

Lastly, Deimos is caring. If we disregard the developed jealousy for a moment, Deimos really does care about Cain (and later- Abel). He went out of his way to replace Cain's cigarettes that got lost when Cain stood up for him and though that may be largely due to his crush, he does care to a degree. Even with the bitterness from breaking off with Cain, he doesn't want to actively hurt Abel either. Perhaps Deimos wanted everyone to turn on Cain in that moment because he felt betrayed by Cain.