Furball was a female nexu that was owned and trained by a human resident of the planet Ruusan. When the bounty hunters Beilert Valance and T'onga visited Ruusan in search of Valance's former mentor, Nakano Lash, the nexu and several residents attacked them to defend Lash. Valance fought back against the nexu, but was stopped by her trainer, who, upon learning Valance's identity, directed them to Lash's location. After the nexu's owner rescued T'onga, who had been shot and nearly killed, he sent a message to the hunter's wife, Losha Tarkon.
After Tarkon arrived on Ruusan, T'onga regained consciousness. She intended to embark on a mission to put an end to the crime war between the Unbroken Clan and the Mourner's Wail Syndicate, wishing for Tarkon to accompany her. The nexu was given to T'onga and Tarkon by her owner to assist them in their quest. Tarkon later took to calling the nexu Furball.