Jaylah was a survivor of an attack by Krall. For years, she lived in the crashed hulk of the starship USS Franklin on the planet Altamid. In 2263, Jaylah helped the crew of the USS Enterprise, after it was destroyed, to fight and defeat Krall, leaving Altamid in the process. (Star Trek Beyond)
Escaping from Krall
Years prior to her encounter with the USS Enterprise crew, Jaylah and her family, like many before them, were attacked by Krall and imprisoned on Altamid. Jaylah and her family quickly realized that people were routinely taken from Krall's holding cells and killed, so they decided to attempt escape. During the attempt, Jaylah and her father were confronted by Krall's subordinate Manas. Jaylah's father stayed behind to hold off Manas, buying Jaylah time to flee at the cost of his own life.
Jaylah discovered the derelict hulk of the Freedom-class USS Franklin and made her home in it. She hid it using holographic technology and set up multiple defensive traps in the surrounding area. Inside the vessel, she discovered a music player, from which she particularly liked music featuring "beats and shouting". She also learned how to speak English from the ship's records. In time, Jaylah became a formidable warrior, skilled in martial arts and in wielding a quarterstaff that doubled as a rifle. (Star Trek Beyond)
Alliance with the Enterprise crew
Jaylah became a scavenger to obtain parts with which to repair the Franklin and leave Altamid. In 2263, she came across Montgomery Scott, who had recently escaped the Enterprise inside an advanced long-range torpedo, and saved him from three rival scavengers. Realizing Scott was an engineer, Jaylah agreed to help him find his crew if he helped her finish her repairs.
One of Jaylah's traps was subsequently tripped by Captain James T. Kirk and Ensign Pavel Chekov. After Scott assured Jaylah the newcomers were his friends, she set them free. Using a transporter aboard the Franklin, Jaylah and her new allies then managed to bring Spock and Leonard "Bones" McCoy to them. The group formulated a plan to rescue the rest of the crew and stop Krall from launching an attack on Starbase Yorktown. Jaylah initially refused to participate, revealing her traumatic history with Krall, but Scott convinced her they had a chance if they worked together.
Jaylah showed the Enterprise crew a makeshift map of Krall's base and explained her own escape method, allowing them to devise a rescue plan. As part of the plan, Jaylah and Kirk, riding a motorcycle, beamed in near the tunnel Jaylah had used to escape and she dismounted once near the inside of the base. While Kirk used the motorcycle, enhanced with Jaylah's traps and holographic technology to create a distraction, Jaylah used a pulse beacon to enable McCoy and Spock to beam directly to the base. She directed the two to the crew's holding pen, then laid down covering fire for Kirk, before being attacked by Manas. The two fought, but neither was able to overpower the other, and an aggravated Jaylah screamed at Manas during the fight. The battle ended with Jaylah on a roof with Manas, and her pulse beacon on the ground below. At a signal from Kirk, Jaylah threw herself and Manas off of the roof, moments before Kirk caught her, resulting in them beaming back to the Franklin together.
After witnessing Krall launching his Swarm ships, Jaylah aided the Enterprise crew in repairing the Franklin for takeoff. She joined the crew in returning to Yorktown, where they found Krall attacking. Jaylah referred to the Swarm ships as "bees", which inspired Spock to realize that the craft must have a cyberpathic connection, and he beamed over with McCoy to find it. After having studied the connection, the crew came up with the idea to use Jaylah's music player to broadcast a disruptive signal into the Swarm ships in order to destroy them. Jaylah aided Scott in setting up the signal and chose the song "Sabotage" for them to use. After the Swarm ships were destroyed, Kirk sent Jaylah and Scott to Yorktown Headquarters to shut off the atmospheric processor and stop Krall from using the Abronath to murder everyone on the starbase. (Star Trek Beyond)
An invitation to join Starfleet
Jaylah joined the Enterprise crew in celebrating Kirk's thirtieth birthday with a party on Yorktown, where she consumed a large number of alcoholic beverages to no apparent effect. She was delighted to hear from Scott that, on his recommendation, she had been accepted into Starfleet Academy. However, she was annoyed to hear she would have to wear a uniform if she chose to attend the institution. Kirk also advised Jaylah that while there were many rules at the Academy, she shouldn't follow them all. (Star Trek Beyond)
"I am Jaylah. And you are Montgomery Scott."
"Come now, Montgomery Scotty."
- - Jaylah and Montgomery Scott, introducing themselves to each other (Star Trek Beyond)
"Aye. That's right. I fix things."
"I know what is engineering!"
- - Jaylah and Montgomery Scott, shortly after meeting each other (Star Trek Beyond)
"You take my house and you make it fly."
"I like the beats and shouting!"
"You sure know how to throw out the welcome mat."
"I do not know what is a welcome mat."
- - James T. Kirk and Jaylah, after he is released from one of her traps (Star Trek Beyond)
"My house is BREAKING!"
"The vent! Get out of there, James T.!"
- - Jaylah, to Kirk when he and Krall are about to be blown out into space (Star Trek Beyond)
"Uh, did you drink all those yourself? I'm impressed."
"Someone said it will take my edge off. My edge is still not off."
- - Montgomery Scott sees a lot of empty glasses in front of Jaylah at Yorktown (Star Trek Beyond)
Jaylah was portrayed by Sofia Boutella.
The character of Jaylah was created in an effort to increase the female quotient in the main cast of Star Trek Beyond. When Simon Pegg and Doug Jung were writing the film, they took inspiration for depicting Jaylah from Ree Dolly, Jennifer Lawrence's character in the film Winter's Bone. Pegg later explained, "Doug and I and [Director] Justin [Lin], in the writing room, wanted to create this very independent female, very resourceful character on the Altamid surface." However, thinking up a name for the new Star Trek character was a struggle. The writing team began calling her "Jennifer Lawrence in Winter's Bone" but that understandably became too unwieldy, due to the length of the name. "It started to get tiring, always saying, 'Jennifer Lawrence in Winter's Bone,'" said Pegg. "It's a long name! So then we started calling her 'J-Law'."  That shortened form was suggested as a joke but caught on, before the name ultimately changed to "Jaylah". Despite the inspiration, Doug Jung, with a laugh, described the connection between Jennifer Lawrence and Jaylah as "so esoteric." Of the latter, he added, "Phonetically, it sounded good – 'Jaylah.' It sounded a little foreign." 
Regarding how Jaylah's persona was invented, Doug Jung stated, "We wanted her character to be someone who was outside of the understanding of the Federation and what it means, and really, to really be a blank slate in the sense that she has no real understanding even of her own people, in a way [....] We thought it would be nice to have a character who can feel the full effect of what it means to be a part of this Federation and this group of people. To adopt their sort of unifying way in which they look at who they are."  Justin Lin agreed, "I knew if we did it right, it would be great to have a new character who could potentially join the family." (Empire, issue 326, p. 76)
Jaylah's make-up was designed by make-up designer and make-up effects supervisor Joel Harlow in collaboration with a team led by Neville Page. The group aimed to make the character's make-up "instantly iconic," which Harlow felt was most important, as well as "instantly recognizable." (Star Trek Magazine Movie Special 2016, p. 81) There were, though, multiple goals that drove the process of designing Jaylah's make-up and costumes. Costume Designer Sanja Hays offered, "She's an alien woman who needed to look interesting, and strange, but also heroic." (Star Trek Magazine Movie Special 2016, p. 41) Sofia Boutella asked Hays to add heels to Jaylah's boots, so her height difference to the rest of the cast would not be a problem. 
As it turned out, the design direction for Jaylah's make-up was suggested by neither Joel Harlow nor Neville Page. "That pale skin, black strip look came from Joe Pepe, who is one of Neville's designers," Harlow divulged. "It was something Justin [Lin] gravitated towards during one of the meetings." (Star Trek Magazine Movie Special 2016, p. 81) A character design by Neville Page and a clay sculpture by Richard Alonzo served as the basis for Jaylah's prosthetic make-up, which was created by Joel Harlow. (Cinefex, No. 148, pp. 85 & 88)
Adapting the selected chromatic facial design into a make-up scheme, however, involved many hurdles, such as making the black lines look the same every time they were applied, on each day of the film's considerably long production period. (Star Trek Magazine Movie Special 2016, p. 81) "The black lines were done sculpturally [on a pretty thin forehead appliance]," Joel Harlow remembered. "It would have been a nightmare to maintain those lines every day, even using a template, so I had the idea of making them slightly raised – that way, we knew exactly where they were." (Cinefex, No. 148, p. 88) Jaylah's make-up was labor-intensive not only due to the effort required to apply the paint, but also because a particular shade of white first had to be selected for the skin color, which called for some trial and error. Ironically, the color that was eventually picked wasn't even truly white. Using a pure white color would have made Jaylah look "clown-like." Instead, a multitude of pale colors was used. This combination gave an overall impression of white because the adjacent black lines were colorized with an absolute shade of black. Applying the various pale shades in different orders would produce slightly different appearances. Harlow said about the pale mix, "In order to make it look like skin, we [had] to break it up as you would a traditional prosthetic. There was a lot of experimentation for what that color combination would be and in what order those colors would be applied." (Star Trek Magazine Movie Special 2016, p. 81)
Jaylah's make-up incorporated a pair of contact lenses and some extremely subtle prosthetics, too. Representing ridges near Jaylah's eyes, the prosthetics stretched from the actress' nose to her forehead. However, the entire bottom part of the face was the actress' own skin, not covered at all by prosthetics. (Star Trek Magazine Movie Special 2016, p. 70)
The white-and-black motif was designed to extend into Jaylah's hair. Thus, there needed to be a seamless transition between the actress' smooth skin, the prosthetic piece, and a custom wig tied by Wigmaker Khanh Trance. "It was important that her skin tone blended into her hair color," said Joel Harlow. "Sonya Hayes, the costume designer, had the idea of raising the ridges between the black lines, which made it all work. I [subtly] airbrushed the black into the recessed areas, continuing the lines and fading it out." (Cinefex, No. 148, p. 89)
The make-up of Jaylah boosted the production staff's confidence in the character. "As soon as we saw the makeup effects they were going to use, we knew it was going to be great," Doug Jung reminisced. 
When she first auditioned for the role of Jaylah, Sofia Boutella had no idea what character she would be playing, nor in what film. "It wasn't until the callback that they told me it was Star Trek, and what character I was playing," she recalled. "Then they took me to the make-up trailer and said, 'This is what you're going to look like.' And I was like, 'Holy shit.'" (Empire, issue 326, p. 76) Boutella, who had never done any prosthetics work before, elaborated, "At first, when I had the make-up put on me, I thought, 'what remarkable work.' I've never seen anything like it." (Star Trek Magazine Movie Special 2016, p. 70)
The prospect of casting Boutella as Jaylah immediately seemed right to Justin Lin. "I knew as soon as I saw her," he recollected. (Empire, issue 326, p. 76)
Boutella approved of the role, not only because she thought being in Star Trek would be "a great opportunity" for her but also thanks to Jaylah's newness. "I was attracted to this character, because she's an alien, and she's a completely original character in the Star Trek universe, so I don't have to compare myself with anyone who came before me. I am Jaylah," the actress attested. (SFX, issue 276, p. 49)
The casting choice of Sofia Boutella influenced the depiction of Jaylah to an extraordinary extent. "Usually when you're writing you try to find someone to fit [what you've written], but I started crafting the character to Sofia's strengths," stated Justin Lin. "I wanted someone who when you meet them has this strength, but you realize it might be a mask." (Empire, issue 326, p. 76)
Though she had never seen a Star Trek film before she was cast as Jaylah, Sofia Boutella watched all the movies once she was given the part and, during production on Star Trek Beyond, she relied on the advice of Justin Lin, a longtime Star Trek fan. "This is why it's so much fun to be creating an original character like Jaylah," she enthused. (SFX, issue 276, p. 49)
Sofia Boutella found the most difficult aspect of playing Jaylah was the character's make-up. "This is not a CG-created character; I spent four hours in make-up every morning," she noted. (SFX, issue 276, p. 49) Boutella additionally related, "There were days where I'd wake up at 12:30am to get make-up before a morning shoot. It's a long but fun process." The actress found the make-up and the lengthy durations it took to be applied helped her get into character.  "When I put on the prosthetic, and saw myself in the mirror," she recalled, "it instantly put me into the character, this alien warrior, along with holding her main weapon, which looks like a stick and which she is very skilled with." (SFX, issue 276, p. 49) Boutella also got used to the make-up. "The more I had the prosthetic on, it was harder to imagine Jaylah without it on. There's weight to it, even if it wasn't that much, and the ponytail has a certain weight [and feel] [....] It would be difficult to play Jaylah without all that going on." (Star Trek Magazine Movie Special 2016, p. 70)
Jaylah's fighting style is dance-like because Sofia Boutella trained as a dancer. (Empire, issue 326, p. 76) "So, she was very up for, you know, the physicality of it," Simon Pegg added.  Indeed, Boutella found her experience as a physical artist was of full benefit to her portrayal of Jaylah. "It was very helpful to use my dancing ability, and what I've learned as a dancer, to execute everything that was required of me," she explained. "I definitely used some of my old tricks, my body language, or treating things as a choreography, or looking at things with a rhythm so I could learn them." Boutella certainly found her dance background helped her with her fight training for Star Trek Beyond. She also used it to try to make Jaylah's presence seem particularly alien, for example being conscious of how she moved, sat and walked while playing the character. To participate specifically in the film's fight scenes as Jaylah, Boutella trained in parkour and bōjutsu. "It was a lot of fun to learn [parkour], to be honest," she admitted, "though at first I said 'I'm never going to be able to do this,' because it's quite hard." (Star Trek Magazine Movie Special 2016, pp. 70 & 72)
Simon Pegg deliberately wrote Jaylah's dialogue in a broken English that was inspired by Sofia Boutella's French accent. (Empire, issue 326, p. 76) Jaylah's way of speaking also referenced Star Trek: The Original Series, Doug Jung recalling, "Simon found a voice for her that was a bit of a wink and a nod to, 'Why is it, whenever they find aliens in the original series, they all speak English? What does that really say?'" (Star Trek Magazine Movie Special 2016, p. 27) Boutella herself said, "I definitely tried not to speak with my French accent. It would be weird for an alien, wouldn't it? Finding [her] language and speech pattern, it was very interesting to discover." (Star Trek Magazine Movie Special 2016, p. 72)
It was Sofia Boutella who thought up the moment where Jaylah assumes the command chair onboard the Franklin, which wasn't scripted but was proposed by the actress when she improvised it on set, during rehearsal. "She came in and sat down, and she said, 'This is my house,'" Justin Lin remembered. (SFX, issue 276, p. 49)
Even Jaylah's friendship with Scott had a real-life parallel. Sofia Boutella observed, "Jaylah and Scotty develop a sort of brother and sister dynamic that Simon and I have off-set." 
As Boutella had expected, the process of inventing Jaylah turned out to be delightful for her. (Star Trek Magazine Movie Special 2016, p. 72)
In Simon Pegg's opinion, Sofia Boutella was successful as Jaylah; he called the actress "a golden addition to this group," referring to the film's principal cast.  Pegg also remarked, "Sofia charmed the socks off of all of us. She inhabits the character in such a way that made it a real joy to be her foil in the film. She's super-resourceful and tough. I love that she has this strange, syntactical way of speaking, which makes her feel very alien, and yet she's unbelievably sympathetic."  Doug Jung described Jaylah as "one of the best characters to write" and went on to say, "She ended up being this fun, wild card character, and great for us, because we got to add a new alien race to the canon." (Star Trek Magazine Movie Special 2016, p. 27) Jung also remarked that not only was Jaylah "kind of great," but also that Boutella "was amazing." 
Producer J.J. Abrams was likewise impressed with how the role of Jaylah turned out, enthusing, "I think Jaylah is my favorite new character. She is this unbelievably spirited, sweet, funny, and tough as hell character that becomes a very important ally to the crew, and Sofia did an incredible job of bringing her to life." Joel Harlow was proud of Jaylah's appearance, remarking, "I think the white and black lines of her make-up, combined with the ribbing on her hair gives her a completely unforgettable look."  Glad that Justin Lin had chosen the black-and-white appearance for the character, Harlow therefore deemed the objective of having Jaylah's make-up design "instantly recognizable and instantly iconic" as having been achieved. (Star Trek Magazine Movie Special 2016, p. 81) Sanja Hays concurred about the character's design, "I think that's probably one of the most successful we've done, Joel Harlow and myself." (Star Trek Magazine Movie Special 2016, p. 41) Uhura actress Zoë Saldana was very impressed by Sofia Boutella's performance as Jaylah. (Star Trek Magazine Movie Special 2016, p. 47)
The first issue of Star Trek: Boldly Go established that Jaylah did accept the offer to join Starfleet Academy. She was shown on Earth at the Academy, listening to a lecture that Montgomery Scott was giving. The fifth issue centered on Jaylah's backstory. She was born in space, from a family of space traders, losing her mother during childhood. An older sister, Keelah (β), died at the hands of Krall the same night Jaylah and her father ran away from the base.
The story also established that the black markings on her face had a meaning - "fierce", from which they derived her name.