Chance Pellegrino has never been the lucky type. Growing up on Christophsis he loved to tinker with things, but as soon as he touched something, it was as good as scraps. Wherever he went, whatever he did, destruction followed. He never actually meant to do wrong, but he just wrecked things, whether it was his dad’s speeder bike or his family droid. When he accidentally burned down half of the house, his mother had enough and sent him on his way.
Being known in town for ruining whatever he laid his hands on, people steered clear of him, and Chance thought he'd never get a job, until a well-to-do traveling merchant, a Bothan named Zubreen arrived in town, and feeling sorry for the teenage boy, took him in. While Chance initially wreaked havoc on the merchandise, during their travels through neighboring planets Zubreen taught him bit by bit how to fix and operate things, from weapons to droids, to planetary and space vehicles. Within a few years, Chance became almost as good at creating and fixing things, as he was at breaking and destroying them, and nothing made him happier than traveling with Zubreen. He also picked up a couple of tricks on how to handle people from his slick master, who became a father figure for him, as the years passed.
Having witnessed the devastation of the Clone Wars and shocked by the suffering Emperor Palpatine's tyrannical rule brought to the galaxy, the Bothan felt inclined to occasionally offer what he could to help the Rebellion, either with some money, useful information, or contacts throughout the Outer Rim. Chance was amazed by his generosity and commitment to help others.
When Zubreen died two years before the battle of Endor, Chance just felt lost. The man who took him in was gone, and he did not feel worthy of taking over his business. Knowing that the Rebellion’s cause was close to his adoptive father's heart, he sought them out and volunteered. The Rebellion had countless wonderful mechanics, and his skills were not put to great use until he realized that he had an even greater talent for something else: wreaking chaos. His idea was welcomed by his superiors, and shortly before Palpatine's fall, he infiltrated the Empire capital ship… and got to work as a mechanic. Soon the Empire's forces were dispersed, but the capital ship continued to fight the emerging New Republic, and so Chance continued his work, too. What he does might not be as spectacular or as heroic as what an ace pilot does. But his work might just be enough to tip the balance in battle. He is part of the repair crews that work on starfighters in the hangar, just like all other mechanics. But when he's done, a single part or fitting might be missing, or assembled in the wrong way, or an undetectable device might be ticking on the fighter. None of that can be noticed until the ship is actually deployed. And since fighters blow up all the time in space combat, who would suspect foul play? And Old Chance is still there, fixing things. Things just have an unfortunate tendency of breaking sometimes.