Mia Desik hails from Ord Mantell. She was forced to become a scavenger at a very young age to survive. Her father was a scrap merchant, and her mother was a space pirate who died in a botched heist when Mia was six years old. She later found out a business associate had sold her mother out, and she swore she would get even. The only memento she had to remember her mother by was her black flag emblazoned with a skull boasting cybernetic implants, floating above crossed bones.
She didn't want to follow in her mother's footsteps, but she liked the idea of space travel, and of fighting. One day she came across an Imperial Navy recruitment flyer, and she decided that was her ticket out of there. The flyer mentioned a recruitment outpost on a nearby planet. Mia decided to save up as many credits as she possibly could before her coming of age in order to afford the trip.
Unfortunately, one of the local gangs caught wind of this, and on a fateful day when her father wasn't home, mugged her and stole her money. She put up a fight, but there were too many for her, and one of the thugs slashed at her face with a vibroblade, cutting a deep wound across her left eye. That experience changed her, and hardened her. When she found out the same business associate that sold her mother out was the leader of that gang, she dedicated all her time and energy to hunting them down—the bastards who flew under the flag of the vulture. She committed the image of that flag to memory and got to work.
Her father, who caught wind of all this, had a heart-to-heart talk with Mia. He had been saving whatever credits he could for years, because he wanted her to have a better life. He asked her to stop her crusade, and, in return, he would provide the credits for her to travel to the academy and join the Imperial Navy. Mia, concerned for her father's well-being, refused at first, but he assured her everything would be okay.
Mia's fire impressed the Imperial Recruiter, who figured she could serve among the infantry. The aptitude test, however, revealed she had a knack for piloting ships, and she was transferred to the TIE Corps academy to begin her training.
Years later, Mia had become an accomplished Bomber pilot. Her official designation was Beta 5, but her fellow pilots always called her Crossbones due to the flag she kept in pristine condition in her quarters. She liked that, and she kept it—even going so far as using it as her official callsign. Her superiors didn't approve, but also never pushed the issue. She did her job well, and that was enough for them.
When reports came in that a warship with a vulture logo emblazoned on its side came in, Mia was the first to request to be included in the mission. Her superiors were surprised that she would take such an unimportant mission, but they allowed it. When all was said and done, Mia had 13 confirmed starfighter kills, and had played a major role in the destruction of the pirate frigate Zelles. The ship's captain was none other than the target of her revenge plot. She relished the screams as the pirates begged for mercy as they cooked inside their own warship.
After the destruction of Alderaan, Mia was dismayed. She had been sold on Imperial forces being the peacekeepers of the galaxy, but the outright murder of billions of civilians to snuff out a Rebel cell was too much for her. At the first opportunity, she took her Bomber and her flag, and deserted. After pledging her services as an escort for an old junk hauler in return for passage to other systems via their cargo hold, she eventually found a rebel cell and convinced them that she aimed to defect.
Many tense months passed as she was forced to turn over her TIE Bomber and was essentially without any bargaining chips. However, with the need for pilots in the rebel starfighter ranks always high, she was eventually allowed to fly on scouting missions and other probationary missions that were either not important or kept her out of a position to do harm if she was a deep plant meant to bring them down from within. After a long and boring year passed in this manner, she had finally gained the trust of her new peers and was fully welcomed into the ranks for full fledged combat missions where she performed admirably.
Mia eventually found her way into Skull Squadron. Her ability to wipe out starfighter squadrons with a bomber armed with multi-lock missiles is short of legendary-as much as the dishes she cooks every now and then. Something her squadmates appreciate a lot.