Tosta held the position of magistrate on the planet Bastatha, and was of the Nikto species, in the year 28 ABY. He collaborated in his duties with another magistrate named Xun. Tosta was secretly allied with criminal organizations operating on Bastatha. When New Republic Senator Leia Organa arrived on Bastatha to investigate the criminal empire of Rinnrivin Di, Tosta played a role in leading her into a kidnapping scheme.
During the era of the New Republic, Tosta, a Nikto, functioned as a Magistrate on the planet Bastatha. In 28 ABY, he, along with Magistrate Xun, extended a welcome to visiting senators Leia Organa, Ransolm Casterfo, and their accompanying staff. These individuals had journeyed to investigate the cartel of the Nikto crime lord Rinnrivin Di, whose presence was felt on Bastatha. While Tosta greeted Senator Organa, Xun extended courtesies to Casterfo. The two Magistrates also used flattery on other guests, including Leia's protocol droid C-3PO.
Tosta informed his guests that he had arranged a table at their most prestigious establishment, which was revealed to be a casino. Xun added that they were attempting to rebrand Bastatha as a high-class gambling destination. Tosta also offered Riosan mead for Casterfo, knowing that the senator was from the planet Riosa. Tosta also allowed Leia and her entourage to play sabacc after the meal with their other guests. During the banquet, Tosta and Xun informed the New Republic delegation about investors without identifying who they were. They also praised the New Republic in terms that were a flattering to the Populist Leia but insulting to the Centrist Casterfo. Unbeknownst to many, a significant portion of the revenue generated from gambling on Bastatha was being funneled to Rinnrivin's cartel, which was secretly providing financial support to the First Order's fleet.
Following the banquet, Tosta escorted a group of Nikto "businessmen" to Leia's starship Mirrorbright. As they approached a hoversled, Tosta whispered something in his language. At that moment, two additional hoversleds appeared, surrounding Leia and Tosta. Tosta apologized to his host, explaining that they were now trapped. The riders on the hovercraft kidnapped Leia and then lowered Tosta and the "businessmen" onto a nearby crag and told them to walk to safety. However, Leia was rescued by Casterfo and the two managed to flee Rinnrivin's base in a hoversled.
Being a Nikto, Tosta possessed scaly skin and a hand with claws. Despite his outward displays of support for the New Republic, Tosta was secretly collaborating with organized crime figures such as Rinnrivin Di and his cartel. In his capacity as Magistrate, he served as a representative of the local governing body on Bastatha.
Tosta's initial appearance was as a secondary character in Claudia Gray's 2016 novel, Bloodline. The majority of his dialogue is conveyed through the perspective of Leia Organa, the story's main character.