Moshene Tre was the un'Yala, or chief, of the Cas'ta tribe of the Rellarin people of Rellnas Minor. As expected of a Rellarin un'Yala, he was a peaceful person, with a strong sense of ethics and justice. Though he had the somewhat fearsome appearance typical of a Rellarin, he was a soft-spoken, gentle being.

At some point prior to 19 ABY, Tre left his homeworld—an unusual step for a Rellarin. He became part of the New Republic Observer corps, an organization sponsored by the Republic to act as independent observers of conditions and crises throughout the galaxy which required the Republic's attention. Like all Observers, he was assigned to a sector far from his homeworld. Tre's assigned sector included the planet Cejansij.

In 19 ABY, as the Caamas Document crisis was leading the New Republic to the brink of civil war, he met with Jedi Master Luke Skywalker on Cejansij. At the time, Skywalker was not involved in the search for the document, or in the efforts to diffuse tensions between the factions who wanted to punish the Bothans for the destruction of Caamas and those which rejected the notion of collective punishment. Instead, he was searching for the source of clones who had appeared in certain pirate groups. All the same, when Tre discovered that Skywalker had arrived in the city of Canyonade on Cejansij, he approached him in order to discuss the crisis.

Together, the Observer, the Jedi Master, and R2-D2 watched a large gathering of Cejansiji in a solemn, peaceful demonstration. This demonstration commemorated the Caamasi, the Vrassh, and several other cultures which were victims of genocide. The demonstration also called for justice for the survivors, though not all of the demonstrators wanted to punish the Bothan people as a whole. Tre wanted Skywalker to see this demonstration in order to emphasize that the Caamas Document crisis was not merely a product of rival political factions seeking influence within the Republic, but that it stemmed from genuine differences of opinion and a widespread desire for justice in the Galaxy.

After they parted, Tre invited Skywalker to meet with some of the protesters later that evening at the ThoughtsAreFreedom tapcafe. However, Skywalker encountered Moranda Savich soon afterward. This chance encounter led to a meeting with Talon Karrde, which led to the news that Mara Jade had been captured on Nirauan. Skywalker hastily left to rescue Jade, without meeting with the Cejansiji protesters.