|Ezri Dax, a Trill female|
|Norvo Tigan, a Trill male|
The Trill (or Trills) were a humanoid species native to the planet Trill. A small percentage of the Trill population co-existed with a sentient symbiotic organism known as a symbiont inside their bodies. The resulting joined Trills had personalities which were a synthesis of the two beings including the memories, and to some extent the personalities, of the previous hosts of the symbiont. This way, the joined being gained all the skills and occupations of the previous hosts. As late as 2367, the fact that some Trills exist as a joined symbiotic species was widely unknown, even to Federation scientists. (TNG: "The Host")
Most Trills are distinguished by two rows of spots going down each side of their bodies, from forehead to toe. Their skin color could vary. One of the main neurotransmitters in the Trill brain is isoboramine. (DS9: "Equilibrium") Joined Trills are also extremely allergic to insect bites; the biochemical connections between the host and symbiont cannot tolerate the reaction caused by the insect's venom. (DS9: "The Siege") One Trill peculiarity is that they are known for having cold hands. (DS9: "A Man Alone")
The few Trills that are given a symbiont are typically joined in their early- to mid-twenties. The physical process of being joined is irreversible. Once joined, the host and symbiont are dependent on each other after ninety-three hours. If the symbiont is removed from the host, symbiont and host will die within hours, even if they are otherwise healthy, unless they are reimplanted with another host or symbiont. (DS9: "Dax", "Invasive Procedures")
The brain of a joined Trill has two cerebral nuclei and two different brain wave patterns. Julian Bashir compared them with two linked computers, which both work for the same task, in 2369. (DS9: "Dax")
Despite the relatively unusual nature of being a joined species, that aspect of their culture was not widely known until 2367, when the Odan symbiont had to be given a new host during the middle of tense negotiations on Peliar Zel. Such a public example of the dual nature of the Trill brought to the forefront what had previously been a very private matter to Trill for several millennia. (TNG: "The Host")
In contrast to the greater revelation of their nature, the Trill are not a secretive species. To them, the joined nature of their culture is normal and not something they would think to comment on without prompting. Indeed, joined Trills can be seen as particularly genial and many have served the Federation as distinguished ambassadors, including Odan and Dax.
Jadzia Dax joked that Trills don't look for romance the way Humans do. Joined Trills consider it quite a nuisance and view it as a weakness of the young. While hosts may have romantic feelings as often as any other sentient species, symbionts try to live on a higher, more spiritual plane and try to rise above those sorts of temptations. (DS9: "A Man Alone")
Trill law forbids reassociation between subsequent hosts of joined persons, whose symbionts were romantically involved in their previous hosts, and the people who the previous hosts were romantically involved with. This is because the main purpose of the transfer of symbionts is to experience new things in life. Trills who are found guilty of reassociation are expelled from Trill society, meaning that their symbionts die with their current host. (DS9: "Rejoined")
On average, only three hundred symbionts are available for hosting each year and about a thousand Trills apply for joining. Because there are many more humanoid Trills than symbionts, prospective hosts are weeded out by a demanding selection procedure, overseen by the Symbiosis Commission. (DS9: "Equilibrium") The competition for the few symbionts is fierce and attracts the brightest and most highly motivated of Trill society. Often the would-be hosts excel in their chosen fields and it is not uncommon for them to hold several degrees or distinctions prior to their joining. Prospective hosts may eventually become initiates under the supervision of a field docent, a joined Trill who evaluates the prospective host's suitability for joining and makes a recommendation to the Commission. A negative recommendation usually means the initiate is cut from the joining program. (DS9: "Playing God")
Common belief in Trill society holds that only one in a thousand Trills make acceptable hosts. In fact, this figure is vastly understated, and nearly half of the Trill population is capable of being joined. The myth is perpetuated very carefully, though, in order to avoid the widespread chaos which would arise if the information were made public, since the symbionts would become, essentially, objects to be fought over, as people fought to gain the few prized symbionts. (DS9: "Equilibrium")
Unless the joined Trill objects, a prospective host may request a specific symbiont. If a host is weak, the personality of the symbiont will overwhelm it. Joined Trills have several tools at their disposal for dealing with various aspects of their previous hosts. The telepathic ceremony of zhian'tara allows a current host to divest the symbiont of the personality and all the memories of a previous host, which are temporarily hosted in volunteers. The transferring process is performed and supervised by a symbiont Guardian, an unjoined Trill telepath. The ceremony creates a chance for closure by having the new host address the previous hosts directly as a means of distinguishing their voices and cementing the sense of finality of its latest transition. Similarly, the Rite of Emergence can focus the voice of a single previous host among the memories of the other, allowing for a more direct conversation in times of need for the current host.
The zhian'tara ritual is roughly similar to the Vulcan fal-tor-pan ritual, since both enable the respective species to perform a synaptic pattern displacement, the transfer of what could be considered as a soul (katra, pagh, etc.). (DS9: "Invasive Procedures", "Facets", "Field of Fire")
In the mirror universe, it was unclear which side (if any) the Trill government took in the conflict between the Klingon-Cardassian Alliance and the Terran Rebellion. A number of individual Trills were part of the Rebellion, while others would attempt to remain non-aligned. (DS9: "Through the Looking Glass")
Ships and technologyEdit
Background information Edit
At the time the concept of Trills was first conceived, the idea was (at least in the opinion of Brannon Braga) "very fresh." Ronald D. Moore suspected that many freelance writers would have centrally featured the Trill in the premise of TNG: "The Host", the first episode to depict a Trill, to a degree more than the installment actually does. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 221)
For the make-up team tasked with designing the look of the Trills, the challenge was threefold: the humanoid host, the abdominal cavity and the symbiont. (Star Trek: Aliens & Artifacts, p. 116) The facial appearance of Trills was originally designed by Michael Westmore for "The Host". "The original Trills had a forehead appliance and a little nosepiece," he said. (Cinefantastique, Vol. 23, No. 6, p. 31) The appliance used for the nose and forehead downplayed the alien nature of the Trills, causing them to seem just slightly extraterrestrial but still overtly human. (Star Trek: Aliens & Artifacts, pp. 116-117)
The requirement of creating a body cavity for the symbiont was much more challenging. The make-up department crafted an appliance for the stomach area, covered with enough hair to blend in with the actor's own body, with three air-bladders beneath the fake skin. Activating the bladders, by air blown into them via tubes, could give the impression that the skin was being moved by the symbiont living inside the host. Since the stomach appliance was made with extremely soft rubber, the pulsating of the bladders was able to swell inside the whole area of the cavity, expanding it noticeably, which made for a very effective shot. (Star Trek: Aliens & Artifacts, p. 117)
At first, Trills were not to have featured as much on Star Trek: Deep Space Nine as they ended up being, because the creative staff initially considered a variety of alien species for the character of Jadzia Dax. "Of them, the Trill seemed the most interesting," noted Michael Piller. (Cinefantastique, Vol. 23, No. 6, p. 20) Once that species was selected, explaining the concept of a Trill to those who auditioned for the role proved difficult, hampering the casting process. (Star Trek - Where No One Has Gone Before, paperback ed., p. 179)
It was initially planned for the Trills of DS9 to look basically identical to Odan, who had established the Trill appearance in "The Host". The make-up was consequently to still consist of several distinguishing marks on the forehead. (Cinefantastique, Vol. 23, No. 6, p. 21) Thus, a prosthetic forehead, much like the original, was shot for two days, with test footage involving Jadzia Dax actress Terry Farrell. "Then they kept reducing it with each test," she related, "until it really looked like someone had just hit me in the forehead. But Paramount didn't want to make me look strange." (Star Trek: Deep Space Nine Companion, p. 7) After Paramount executives watched the dailies of Farrell in DS9 pilot "Emissary", they issued a rare ultimatum about the Trill make-up. The executives insisted the make-up be changed via removal of the forehead markings; having spent a long time seeking a beautiful actress for the role of Dax, Paramount wanted to avoid Farrell being defaced by prosthetics. (Cinefantastique, Vol. 23, No. 6, p. 21) This finally resulted in the more common spots seen on Deep Space Nine. These were inspired by Kriosian make-up from TNG: "The Perfect Mate". (Star Trek: Deep Space Nine Companion, p. 7) The reasons for the change were purely cosmetic and the writers of DS9 were aware of the contradiction, but no canon explanation has ever been offered. After she had put on the Odan forehead appliance, someone looked at Terry Farrell and said to Michael Westmore, "What did you do to her head, she used to be beautiful?" Westmore then suggested to "just give her spots like we gave Famke," who played a Kriosian. This makeup was used on all Trills afterwards. (Star Trek: Deep Space Nine Companion)
However, the disparity between Trills seen on TNG and the later Trills goes beyond makeup. "The Host" seemed to make it clear that the symbiont was dominant (in fact, the symbiont is referred to as a parasite on more than one occasion), and that the host was merely a body with no influence over the joined entity. Odan was apparently unable to safely use the transporter, while Dax used it often with no trouble at all. Odan was ready to pick up where he/she and Crusher had left off, despite the Trill taboo against reassociation.
In an attempt to explain the differences in Trills, Terry Farrell once suggested that the spotted members of the species were from the north of Trill whereas Odan was from the planet's south. (Cinefantastique, Vol. 23, No. 6, p. 21) She also regarded the spots as natural-looking. "It's not much different than freckles or leopard spots or zebra stripes," Farrell observed. (Hidden File 05, DS9 Season 1 DVD special features)
Michael Westmore used brown make-up for the Trill spots, and accented them with orange. He never used a stencil, so the spots were always unique.  "It's a laborious job," he remarked. "There seems to be no easy way to make up a stencil for that. It just has to be done every day." (Cinefantastique, Vol. 23, No. 6, p. 31) Terry Farrell stated, "Michael Westmore [...] [used] two different colours of watercolour. The first season we experimented with art pens, but they would take me two or three days to get off of my skin – not pleasant!" Applying the spots generally took slightly longer than an hour each day, though Farrell thought the process would likely have taken less time if she and Westmore hadn't enjoyed conversing with one another quite so much as they did. (Star Trek: Deep Space Nine Companion, p. 7)
Though Star Trek: Deep Space Nine Companion (p. 86) pretends the DS9 writers occasionally used a handbook called "Everything You Always Wanted to Know About Trills", details about the species were actually established as and when required, such as for the DS9 episode "Invasive Procedures". "In this case, it was important to establish how difficult it was to get a symbiont," recalled Robert Hewitt Wolfe, who was credited with co-writing the installment. "It said something about [...] the Trill culture that was interesting." The method of inventing additional aspects of the species also resulted in the writers later revealing, in the DS9 outing "Equilibrium", that it wasn't as hard to qualify for a symbiont as the Trill populace had been led to believe. Regarding the improvisational system, Ira Steven Behr commented, "It's dangerous but fun. The whole Trill concept is very difficult, but 'Invasive Procedures' dealt very successfully with it." (Star Trek: Deep Space Nine Companion, pp. 86-87)
The notion of structuring the DS9 episode "Playing God" around a storyline about Trills, featuring Jadzia Dax and a Trill initiate, was suggested by Michael Piller. (Star Trek: Deep Space Nine Companion, p. 126) Jim Trombetta, who wrote the story, recalled, "I had a little trouble writing that because I didn't really believe there was anybody that wanted to have a worm inside their body [....] [The DS9 staff writers] said, 'No, we've gotta have it. It's an alien race; it means something different to them than it does to us.'" (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 70) Ira Behr commented, "I thought it [...] was an interesting show about Trills." (Cinefantastique, Vol. 25/26, No. 6/1, p. 105)
Another DS9 installment that features the Trill species is "Equilibrium". For Robert Hewitt Wolfe, the opportunity to explore Trill society in that episode intrigued him. Wolfe especially enjoyed how the installment demonstrates that the Trill were meant to be considerably unpredictable and different from Humans. "I think the culture is more complicated than that," he explained, "and I think this show demonstrates that complication, which I like." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 84) Ira Behr also approved of how the Trill were developed in "Equilibrium". "It's a fascinating subject. So fascinating it's deep waters to get into. I just love the scene with the guardian and the Trills–weird kind of stuff we don't quite understand. I also like a society that's basically medical. Its a bunch of people really involved in their bodies." (Cinefantastique, Vol. 27, No. 4/5, p. 95)
Dating First Contact Edit
It is not known when Trills and Humans made First Contact, but Tobin Dax once met the famous Cardassian poet Iloja of Prim while the latter was exiled on Vulcan, indicating Trill and Vulcan had contact prior to 2245. (DS9: "Destiny")
Emony Dax is known to have visited Earth in the mid 23rd century, where she was apparently close to Leonard McCoy. (DS9: "Trials and Tribble-ations") Travis Mayweather mentions having visited Trillius Prime, but it is not made explicitly clear if this is the same planet as the Trill homeworld.
A link between the Trill symbionts and the alien parasites seen in TNG: "Conspiracy" is suggested in the non-canon DS9 short story "Sins of the Mother" (in the anthology The Lives of Dax) and the novel Unity. This was expanded upon in Worlds of Star Trek: Deep Space Nine, Volume 2. The neural parasite was first seen as it traveled in a comet passing close to the Trill homeworld. Audrid Dax and her husband, Jayvin Vod, went to the comet with a Federation team to examine it when Trill scanners showed a being similar to a symbiont in the comet. However, as the Federation was not yet aware of the Trill's symbiotic relationships, it was kept in secrecy. Upon coming into contact with the chamber of the parasite, it bonded with Jayvin, as well as the Vod symbiont, ultimately causing both of their deaths.
The inconsistencies between TNG and DS9 Trill were dealt with in the novels by suggesting that ridged Trills and Trills who could not be transported were subgroups of Trill society; both were mentioned or shown during the scenes on Trills, and the inability of some Trills to be transported was a plot point. In the DS9 Relaunch novels dealing with Trill, the ability or inability to be transported is shown as simply a difference between various Trill ethnicities.
The comics took a far different course, such as the Star Trek: Divided We Fall mini-series, where the fact is completely ignored. In fact, both Odan hosts are shown, without facial ridges but with spots. All Trills in the series are shown with the spots instead, no reasoning given.
In another novel, Forged in Fire, the ridged Trills are said to result from a strain of the Augment virus that managed to infect a Trill colony through visiting Klingon traders. However, those Trills did not seem to be interested in working on methods of restoring the original Trill look, with this "sub-group" having recently (at the time the novel was set) being re-accepted back into Trill society. This division among the groups possibly explains why Odan was so different from other Trills encountered in the series. The novel also notes that the Trill avoidance of transporters was actually a means of avoiding the nature of the symbiote being disclosed rather than the process being dangerous to the symbiote.