The Odenji were a sentient species that originated on the planet Issor, sharing it with their related kin, the Issori. Initially, they were a traveling underwater group, but after the Issori found them, they moved to land, creating a combined society with the Issori. Together, the two groups thrived and spread to other parts of their native star system, eventually being discovered by the wider galactic world. Because they had both gills and lungs, they could live both on land and in water; instead of a nose, each Odenji had four scent-detecting skin flaps. The Odenji went through a long period of widespread depression called the melanncho, which greatly reduced their population. After this terrible time, they became a sorrowful and pathetic species, rarely showing happiness and taking a more indifferent stance in their homeworld's community. Individual Odenji continued to experience personal melanncho even after the species-wide depression ended.
The Odenji were a sentient species of aquatic, two-legged creatures of average size, without hair, typically standing between 1.5 and 1.8 meters in height. This species was physically suited for underwater living, possessing both gills and large, webbed hands and feet, but they also had lungs, enabling them to live and breathe comfortably on land. Odenji had a typical, upright humanoid stance, with two arms and two legs; the former ended in hands with four fingers. These limbs made them proficient swimmers. An Odenji's face featured two large black eyes located above four flat, horizontal sections of skin that served the same purpose as a nose for smelling. The species also had a projection on each side of their chin. Their skin was smooth, with colors ranging from dark brown to tan. They were related to the Issori species, sharing their homeworld with them.

The Odenji began as a nomadic group that lived entirely in the oceans of their homeworld, Issor, using old-fashioned technology to survive. This changed when the Issori discovered the Odenji and convinced them to move their entire society to the land. There, the Issori and Odenji coexisted, sharing the Issori's more advanced technology and eventually creating a space program that allowed them to colonize other worlds. The joint society in which the Odenji lived was governed by the Tribes of Issori and Odenji, which also governed the worlds the two species colonized. After the Odenji and Issori connected with the rest of the galactic world, they brought in large amounts of technology from other places, catching them up with other cultures. For the most part, the Odenji allowed the Issori to manage all trade with the galactic community, although they still helped produce the goods that were traded.
During the time of melanncho, depression and violent crime reached unprecedented levels among the Odenji. After this disastrous time, the Odenji became a sad and pitiful species, with few ever showing happiness, joy, or humor except with very close friends or family. Because of this sadness, most Odenji acted in an extremely indifferent way, and many refused any positions of power. Despite this outward behavior, many Odenji wanted to be more joyful, and some dedicated their time to pursuing happiness against seemingly impossible odds. Any Odenji could fall into a personal melanncho after a tragic or disturbing event in their life, including the death of a friend or family member. When some Odenji came to believe that the melanncho had been caused by the species' move away from the oceans, they went back to their watery home, rejecting all technology beyond the old-fashioned devices their ancestors had used underwater.
Originating from the world of Issor in the Outer Rim Territories, located within the Issor system of the Arkanis sector's, the Odenji's initial culture was nomadic and entirely aquatic. They lived this way until their land-dwelling Issori relatives discovered them, sharing their old-fashioned technology with the water-based beings. The Odenji were then convinced to move their society onto the land, leading to the two species living together in harmony and working together under a combined Tribes of Issori and Odenji. Within a few centuries of the two species working together, they had reached information-level technology due to a greatly increased rate of scientific advancement. Together with the Issori, the Odenji started a space program to look for other intelligent life, and soon the two had colonized all of the other planets within their system, including Trulalis, where they established dominance over the Human population living there. The region of space containing Issor was first widely explored between 20,000 BBY and 15,000 BBY, and some years after the Odenji and Issor space program had begun, they were contacted by a Corellian scout team who landed on their planet. Although initially surprised to find other sentients, the two partner species quickly joined the galactic community and gained access to far superior technology than their own. The Issor system became the economic powerhouse of the entire Arkanis sector in terms of legal trade, with Issor becoming an industrial world. During the period between 11,000 BBY and 12,000 BBY, the Odenji's homeworld fell within a region controlled by the Galactic Republic, but by 1004 BBY it was within the region known as Hutt Space, which was controlled by the Hutt species, and itself part of Sith controlled space during the New Sith Wars.

Several centuries before 0 ABY, the Odenji were nearly destroyed during a period known as the melanncho, in which they suffered an unexplained species-wide sadness. The sadness was so intense in some individuals that it drove them to insanity and eventually death. The Odenji survived, but despite the Issori's attempts to help, their population was greatly reduced, leaving the Issori as the far more numerous species on their shared homeworld. Even after the species-wide melanncho subsided, many individual Odenji continued to experience it, and various theories eventually arose as to what had caused the great depression. Some believed that the Odenji had been infected by a virus or strain of bacteria, and that the sadness was a symptom of the disease. This view was held by the Issori smuggler Fahs Oxsor, who mentioned the melanncho when his friend Toob Ancher came down with the disease known as Bitter Winter, which was similar to melanncho. Some Odenji began to believe that the depression had been caused by their move from the sea, and as such, small communities of Odenji began to move back underwater, much to the horror of the Issori. The region of space in which the Odenji lived was taken over from the Hutts by the newly formed Galactic Empire in 19 BBY. A new theory as to the cause of the melanncho period was created by Imperial scientists, who claimed the depression was merely a genetic defect in the species that would have wiped them out had it not been for the intervention of Human medicine. Issor was no longer considered to be in Imperial space by 4 ABY. In the year 25 ABY, the Odenji homeworld fell within a region of space with an average population per planet of between one million and ten million sentients. By 137 ABY The Odenji's homeworld fell within the Galactic Empire of the Sith Lord Darth Krayt.
Some Odenji did leave their homeworld and travel the galaxy, although not in as great numbers as the Issori. Those who did leave could often be found on ocean worlds or in marine-related professions. Odenji who began suffering from melanncho while away from home would usually return to Issor and spend the remainder of their days living in the planet's oceans.
The Odenji were first mentioned in "A Bitter Winter," a short story written by Patricia A. Jackson and published in 1995 in Star Wars Adventure Journal 5. The species later received an entry in the Alien Encounters article series, which was written by Brian Smithson and published in Star Wars Adventure Journal 13. This entry included roleplaying stats for the species to use in the West End Games Star Wars: The Roleplaying Game, and an image of the species. A shortened version of the Alien Encounters article entry was included in 1998 in Alien Encounters, a book compiled by Paul Sudlow, which also included a new illustration of the Odenji.