The biography of Jadzia Dax has to take two parts; that about the symbiant "Dax" who is around 300 years old and has had a number of hosts over the years, and that of the humanoid Trill woman, Jadzia.
Lieutenant Commander Jadzia Dax is a 'Joined Trill' which is a union of two species living together as one. She was assigned to space station Deep Space Nine as a science officer in 2369, and started her commission as Lieutenant, and was promoted to Lieutenant Commander at the end of her third year aboard. While Jadzia is a young and beautiful woman, her symbiant Dax, has a rather colorful history, having been joined to no less than seven other hosts, including a murderer, in it's lifetime.
The host before Jadzia was Curzon, whom was a great mentor and a close friend to Benjamin Sisko in his youth. Jadzia had wanted to become a host ever since she was a child and worked very hard at winning the honor. She won scholarships, achieving Premier Distinctions in exobiology, zoology, astrophysics, and exoarchaeology before she finally was joined in 2367.
Before being accepted for joining she got kicked out of the Trill-program by Curzon Dax, but entered again and achieved being the first Trill-joined to re-enter the program. Ironically, the very one that expelled her from the program died, and Jadzia took over the symbiant. She also remains in superior physical condition, and enjoys traditional Klingon marital arts, which she began studying immediately after her joining with the Dax symbiant. She has also found a near match in her combat expertise with Lt. Cmdr. Worf, with whom she has also fallen in love and gotten married to.
In the episode "Facets", she underwent a ritual in which the memories of each of Dax's past hosts are telepathically transferred to another person so she came to understand them better. previous hosts as seen in Facets are...
1. Lela (Major Kira)-Legislator;
2. Tobin (Chief O'Brien)-Mathematician;
3. Emony (Leeta)-Gymnast;
4. Audrid (Quark)-Symbiosis Comm. head
5. Torias (Dr. Bashir)-Short-lived;
6. Joran (Capt. Sisko)-Insane musician;
7. Curzon (Odo)-Federation ambassador.
Jadzia Dax is the trill entity formed by the host body, Jadzia, and the invertebrate symbiont Dax. Although the two live symbiotically as one being, sharing memories, sensations, emotions and experiences, the Dax symbiont is actually much older than Jadzi a , having already inhabited at least five previous hosts. The combination of Jadzia and the Dax symbiont produced a confident, intelligent, and highly respected Starfleet officer who served with the crew of Deep Space Nine from 2369 to her untimely and nee dless death at the hands of the Bajoran Pah Wraith and Gul Dukat.
In her too short life, Jadzia Dax faced death many times. In 2370, she nearly died when a Trill named Verad briefly stole her symbiont in an enforced surgical procedure made possible by empl oying Klingon mercenaries to commandeer DS9. Following the restore of Starfleet control, the symbiont was returned to Jadzia before she suffered permanent injury. Later the same year, she joined Klingon commanders Kor, Kang, and Koloth on the planet Sec arusiv IV to honour Curzon Dax`s blood oath of vengeance against the mercenary of Albino, who had killed Crzon`s godson - Dax son of Kang. Jadzia Dax personally engaged in hand to hand combat with the feared mercenary, and was victorious. More recentl y, Jadzia was wounded and almost died on an undercover mission with her Klingon husband, Worf, when the pair engaged on a phaser battle with a Jem`Hadar patrol. Only Worf's decision to forsake the mission and rescue his near-death wife saved Jadzia`s life.
As well as being an exemplary Starfleet officer, Jadzia Dax had an exuberant social life. Regarded as something of a night-owl, Jadzia often threw surprise birthday parties for her DS9 friends. She had several hobbies, including Galeo-Mandala style wre stling, collecting the music of lost composers, and playing Tonga as well as earth chess with Ben Sisko. Perhaps as a result of the Dex symbionts many lifetimes of experience, Jadzia Dax disliked what she regarded as blind compliance to society's norms and she occasionally enjoyed indulging in inappropriate behavior (such as playing Tonga) for it'e s shock value. Like Curson Dax she had great fondness for Klingon food and Klingon music and she enjoyed playing practical jokes on her colleagues on several occasions in early 2372, she broke into Odo`s quarters while he was regenerating and moved all his furniture very slightly, just to annoy him! an enchanting witty and veracious personality, Jadzia will be greatly missed on board DS9.
Jadzia Dax meets up with her husband from a previous life 'Rejoined'
Jadzia joins Worf and Kor on an expedition to find ... 'The Sword Of Kahless'
Jadzia's husband, Lt. Cmdr. Worf