Kareel joined with the Jer symbiont while serving at OP 42 after many years of being passed over by the Symbiossis Commission.
She is the sixth host for the Jer symbiont.

Maldan Jer- First host, male. Space explorer among the crew responsible for first contact with the Federation. His ship was destroyed in an Ion storm, and Maldan spent months alone inside and escape pod. Being the first host, he had no other host memories to reflect on during his isolation and felt the full force of the isolation. Once he was rescued his months of isolation had taken their toll and his mind was never the same. He was always wearing his emotions on his sleeve and was quick to anger or loose his cool. He was retired to a quiet desk job on the home world where many still saw him as a hero despite his deficiencies.

Ulstan Jer- second host, male. With Jer’s knowledge and interest in the Federation, Ulstan took over where Maldan left off. He became the liaison with the Federation and eventually the first ambassador from the Trill home world. Ulstan was instrumental in bringing the Trill home world into the Federation. Perhaps, as a hold over from the experience with Maldan being trapped inside the escape pod, Ulstan was very protective of the Jer symbiont almost to the point of hypochondria. While serving at the consulate he met and fell in love with one of the members of the staff, a young woman named Merial. It was a very passionate relationship for them booth. The had a large family of seven children. Four sons and three daughters.

Kamath Jer-third host, female. Being the first host of an opposite gender is always a process that takes time to get used to and Kamath’s joining was no exception. Kamath served as an level headed engineer aboard a Federation starship prior to being joined. After joining, the Symbioses commission was not keen on having host serving aboard a starship in a situation that might jeopardize the life of the symbiont. After experiencing problems adjusting to the new male influences in her life and the strong emotional swings she reluctantly agreed to give up her career.
She spent her years acting as a docent and training candidates. She married and had two children, Tylel and Ledo. Ledo later became joined with the Pel symbiont.

Lindth Jer- fourth host, female. Lindth had all the passion and fire of her other predecessors, but with a stubborn streak to match. When the commission wanted her to give up her position as a Starfleet medical officer, she refused and continued to serve in Starfleet. Lindth had several romances but never married as the love of her life died tragically during a first contact mission. She was the first Trill to have a position as an instructor at Star Fleet Academy. She was known for inspiring young cadets, but those who failed to live up to their potential often received one of her fiery tirades that was reminiscent of the rantings of Maldan.

Hegiv Jer- Fifth host. Merchant, father of three. Two sons and one daughter. He was a successful business man, but was not above using diplomatic contacts made by previous hosts. In four lifetimes, Jer had friends or family in nearly every spaceport which could be called upon to help arrange trades or get the inside track on a lucrative deal. Hegiv often found his own ambitions thwarted by the ready emotions from Jer that in previous hosts had been given free reign, but for Hegiv could be like a tell in a game of high stakes poker. After nearly losing his business, Hegiv sought the counsel of Dr. Zar. Zar had helped him gain control of the maelstrom of emotions that went along with joining with Jer. After therapy, Hegiv was able to start putting his business back together and eventually married. It was after the birth of his third child he was diagnosed with a rare disease for Trills, Darnay’s disease. After extensive tests ensuring that the symbiont was not infected or harmed by the disease, Hegiv started to seek his successor. The search took years as he continued to degrade.
Shortly after the 20th birthday of his youngest daughter, Hegiv came across the candidate profile for Kareel Tash, who had been overlooked by the Symbiosis Commission. After much arguing with the counsel, Hegiv was finally given approval to contact Kareel to see if she could be the next Jer host. Upon meeting her in person Hegiv, began to have doubts that she would make a good host for Jer, but certain qualities she possessed impressed him. He felt reassured that her calm disposition would be an important balance for the emotional hosts that had caused him difficulties when he had first been joined with Jer. Hegiv tested Kareel by trying to check her emotional control and make sure that it wasn't merely a lack of emotion that gave her the calm disposition he sought for the Jer symbiont. During these period of testing Hegiv appeared to be very impatient, overbearing and self centered to try to evoke anger in Kareel. This made Kareel doubt if she wanted to have that sort of personality imparted to herself and seriously considered turning down being joined with Jer and drop out of the Initiate Program all together. But before she could realize the implications of the test and be assured that Hegiv was not really what he seamed, Hegiv had a fatal attack from the Darnay's disease and died. Kareel was forced to make the decision to risk putting the Jer symbiont in danger if another host was not found or to go ahead and do what she had been prepared to do and and worked toward and looked forward to doing up until the time she met Hegiv.

Now as one of the newly joined, Kareel must use her initiate training to separate her memories from those of the previous five hosts.