Spero was a Ho'Din of male gender who resided in the Southern Underground of Coruscant.
Leia Organa was responsible for saving his life and the lives of his family members sometime before 3.5 ABY.
While living in the Southern Underground, he ran a plant shop. He cultivated relationships with individuals connected to the Empire, the Rebels, and various criminal organizations, gaining notoriety among smugglers such as Lando Calrissian and Dash Rendar.
Having cultivated a unique strain of yellow fungus that would eventually be used throughout the galaxy, he earned the title of Master Gardener. Within his shop, he also cultivated feather trees.
On one occasion, Leia, disguised as Boushh, visited his shop to "collect" a debt owed to Leia. The disguised bounty hunter sought information about the Black Sun, and Spero shared his knowledge: it was under the control of the powerful Falleen Underlord Xizor, who also owned Xizor Transport Systems. He further revealed that his palace extended far beneath the planet's surface. This confirmed Leia's suspicions, and she informed him that his debt was considered paid. Spero, recognizing her true identity, responded that his debt to her was significantly greater.
Later, Lando Calrissian and Luke Skywalker sought his assistance, only to discover him bound in his shop. They faced an attack from members of the Black Sun and were rescued by Dash Rendar, though Spero was left behind with an apology.