Basil was born into slavery. He was assigned to a spice farm along with many other slaves. Basil's main duty was to harvest a huge field of basil plants (hence his slave name) with a human slave named Rosemary (who was assigned to the rosemary field until she was moved to this field).
Constant abuse and mistreatment was not uncommon. The rebellion was trying to buy/sell resources on "insert planet name here" when Basil's master reported them to the Empire. Rosemary confronted the master, telling him that he was wrong to do so, and was then beaten to the brink of death. Basil was standing behind the master, sheers in hand, he charged up and stabbed him in the back. He then carried Rosemary, running as hard as he could, to the rebel ship. Begging them to save her, they allow him aboard.
Basil watched as the Mirialan rebel frantically worked to save his dear friend. Unfortunately, he was not able to save Rosemary but gained Basil's loyalty because he tried. After a week of mourning his good friend, the Mirialan rebel, now introducing himself as Chaska Hastiin, took Basil under his wing, briefly trained him how to shoot and use a sword, bought him some stuff, got him tattoos signifying his life so far and brought him into the Rebellion.

Freedom: Basil can't stand how the Empire discriminates against all other races, thinking that humans are the best race. He doesn't necessarily hate the Empire other than the racism.

Personnel: Basil has a deep care for any ally of the Rebellion and values their lives over anything. After losing a childhood friend when he was young, he will do anything to save a life.
His duty is accomplished if every savable party member (and other important
NPC) survives the mission.

5 Duty