The Rift Alliance was a group of powerful worlds united by their shared protests at Republic "incompetence" and their threat to secede. Losing any one of these planets would have been a catastrophe for the Republic; losing all of them would have caused the Republic's collapse.
Rift Alliance member Alauni represented Saleucami, the Republic's most powerful trade hub in the Outer Rim, while Aeten II--Diab Duin's world--produced vital ores and crystals for Republic fleet construction. As tensions with the Empire rose, supplies of the healing fluid kolto from Manaan--Shuuru's world-- became indispensable. The planet Erigorm, represented by Augin Blaesus, recorded and administrated the Republic's finances for centuries; its secession would have destroyed the Republic's financial markets.
Not all members of the Rift Alliance were hostile toward the Republic, however. Tai Cordan, a member of Balmorra's exiled government, claimed to be seeking powerful allies to help his home. Senator Tobas Grell and his daughter Nadia, representing the planet Sarkhai, joined out of curiosity.
Supreme Chancellor Janarus knew how devastating the loss of these systems would be and recruited the Jedi Master known as the Barsen'thor to keep them with the Republic. The Barsen'thor would ultimately rally the Rift Alliance into a formidable army to battle the Children of the Emperor, culminating in a showdown against the First Son at the climax of the Battle of Corellia. After Janarus' assassination, his successor, Supreme Chancellor Leontyne Saresh, authorized substantial reparations to the Rift Alliance both in response to their original protests, as well as in gratitude for their efforts to preserve the Republic.
It is interesting to note that while the Rift Alliance was nominally a separatist movement, at least half of the members of the Alliance were not secessionists. Balmorra and Manaan were neutral worlds, who were not members of the Republic to begin with, while Sarkhai had no apparent intention to secede, as its representatives joined only out of curiosity.
- Star Wars: The Old Republic (First appearance)