Star Trek: Deep Space Nine

Ezri Dax was a joined Trill, the ninth host of the Dax symbiont and served as counselor aboard Deep Space 9, beginning in 2375.

(DS9: "Image in the Sand", "Afterimage")

Dax, formerly Ezri Tigan, was born on New Sydney. Her mother was a successful mining magnate, and she and Ezri disagreed on many occasions. Her father was often absent – Ezri noted it was because he couldn't bear to be around his wife. Ezri's closest family member was her brother, Norvo (who gave her the nickname Zee), while her older brother, Janel, was someone she looked up to. Ezri wanted to escape her family, and eventually managed to do so by joining Starfleet.

(DS9: "Prodigal Daughter")

In 2375, Ezri was an ensign serving as assistant ship's counselor aboard USS Destiny when it was dispatched to Deep Space 9 on a medical emergency – to carry the Dax symbiont back to Trill following the death of its previous host Jadzia Dax. En route, the symbiont took a turn for the worse, and, as the only unjoined Trill aboard, though one who had not trained for such a thing yet, Ezri had little choice but to undergo the joining procedure, with only a fifteen minute lecture from the ship's non-Trill surgeon to prepare her.

Following the joining, Ezri returned to Trill with the Destiny, and met with members of the Symbiosis Commission's Evaluation Board, who gave her counseling on how to deal with her new memories, but they were unable to help her further.

Seeking some sort of link to the person she was now, Ezri sought out Benjamin Sisko, a friend of Dax's previous two hosts, to see if he could help her through the difficult process of integrating eight lifetimes of experience. At the time, Sisko was searching for the Orb of the Emissary, and Ezri agreed to accompany him, Jake, and Joseph Sisko, to Tyree to find it, noting "it'll be just like old times... except, different". It was while traveling there that Ezri discovered she now suffered from space sickness – warp drive made her 'a little queasy'.

(DS9: "Shadows and Symbols")

At that point, Sisko returned to Deep Space 9, taking Ezri along with him. She found Jadzia's former colleagues still grieving for her, and was prepared to return to her duties aboard the Destiny, hoping to reduce their pain in seeing her.

(DS9: "Afterimage")

When Kor visited the station, seeking a command in the war, Ezri once again found herself having difficulty separating herself from Dax's previous hosts, wanting to go off with him, fighting side by side.

(DS9: "Once More Unto the Breach")

Quark was very taken with the young Trill, as he had been with Jadzia, and continued to pursue her for many months.

Ezri accompanied the USS Defiant when it resupplied the Starfleet position at AR-558 in the Chin'toka system.

(DS9: "The Siege of AR-558")

Following the events at AR-558, Ezri attempted to assist Nog in dealing with the trauma of losing his leg in the attack. However, Nog's post-traumatic stress caused him to seek comfort in the Vic Fontaine program, rejecting other's efforts to help.

(DS9: "It's Only a Paper Moon")

When Vic's program triggered a secretly-embedded jack-in-the-box subroutine, Ezri helped in the plan to restore the scenario to normal.

(DS9: "Badda-Bing, Badda-Bang")

Not long after, Ezri encountered Captain Boday, the Gallamite, who had dated Jadzia for a short time.

(DS9: "Penumbra")

Following the destruction of the IKS Koraga, and the disappearance of Worf near the Badlands, Ezri found herself once again struggling to separate herself from the memories of Dax's previous hosts.

(DS9: "Penumbra")

During their captivity, Ezri soon realized that Worf was seeking a relationship with her in an attempt to recapture that which he had with Jadzia.

(DS9: "'Til Death Do Us Part")

Ezri and Worf were taken to Cardassia Prime, where it was intended that they would face trial and execution for war crimes soon after.

(DS9: "Strange Bedfellows")

Ezri later helped Worf determine the correct course of action to take following Gowron's disastrous attempt to take control of the Klingon defense strategy.

(DS9: "Extreme Measures")