Although the Bothan is eager for power and will do a lot to achieve it, Borsk has been very useful to the Rebel Alliance. He sits in the Provisional and Inner Councils, where he works with the Alliance's leaders to come up with ways to keep peace in the galaxy.
As a Bothan, Borsk has the traits known to his species. He is short, and has creamy fur. Although he is Bothan, Borsk was born on the colony of Kothlis. Being hungry for power is another sign of the Bothan people, who communicate not just by speaking, but also by ripples in their fur. These ripples and are only fully understood by other Bothans.
It was just after the Battle of Yavin that Borsk brought his faction to the Alliance. This was at around the time the Mon Calamrians joined the Rebels. The Bothans were wary of the Calamarians, thinking them too ambitious. As a result, Ackbar found himself constantly fending off Borsk's attempts to gain a higher position in the Councils. But although he was tiresome within the Alliance's infrastructure, it was Fey'lya's people who found the plans to the second Death Star. The Bothans broke the Imperial code and found out much information, although many perished in the attempt.
His rivalry with Ackbar never stopped, not even when the Calamarian became an Admniral. Borsk, to the astonishment of the other Alliance leaders, was in fact elevated to the position of one of Mon Mothma's most trusted advisors. The Bothan used this position to his advantage, and give years later managed to score a victory against Ackbar. The Calamarian was arrested for military mismanagement during the Battle of Sluis Van, after Borsk uncovered evidence pointing to this fact. Naturally the evidence was fake, and Akbar was cleared. But the Bothan, along with one of his aides, turned to Garm Bel Iblis, a Corellian Senator who had had a falling out with Mon Mothma. He was waging his own war against the Empire, and Borsk decided to throw his chips in with the senator.
At the battle for the Katana fleet, though, Borsk's true colours showed through. On board his escort-frigate, Qenfis, Feyl'ya saw that the Empire was winning, and ordered the retreat of his ship. This left Han, Lando, and Rogue Squadron stranded. Luckily they managed to escape, and Leia and Talon Karrde made sure that Borsk would answer for his actions. They exposed his disregard for his own people, and the Bothan was placed under military arrest, whereupon he was sent to Coruscant to face the Provisional Council.
The Council granted him a pardon, and he was allowed to retain his seat, but he had lost much respect, power, and support. Shortly after all this, he demanded that the Alliance destroy Mount Tantiss and the cloning facility. He pleaded with them when they refused, and offered Karrde 70,000credits to make sure there was no trace of it left. Leia became suspicious, and upon asking, the Bothan just gave a few vague reasons.
To this day no-one knows why Borsk was so insistent, but it must have been because of something that would harm his people. There are some secrets best left unsaid.