R4-T3 served as the personal astromech to Jedi Master Krugen during the clone wars. As the Astromech started showing it's wear and tear he took to calling it "Rusty". Krugen was often tasked with tracking down Jedi and Sith artifacts in far off corners of the Galaxy. As such they spent a lot of time mucking through harsh environments looking for these artifacts. Krugen could never get the hang of his astromech's beeps and whistles and so had him outfitted with a low cost voice modular he bought off of a toydarian on Tattoine. He never could get it off of the "nerf herder" setting though.
When Order 66 went through Krugen and Rusty were shot down over an uninhabited forest planet by their clone escort. Both survived the crash, but not unscathed. The ship was totaled and Krugen badly hurt. Rusty did what he could to aide his wounded master but it was not enough. Eventually he died, still trapped in the wreckage.
Rusty then went to work trying to repair the ship. After a month he gave it up for lost and then started repurposing it for his survival, giving himself combat modifications and building defenses for when those "vat tube loving clones" came for him. They never did. Many years went by before he saw another human. They were Alliance scouts looking for a location for a new Rebel base. Fortunately he recognized them as not being clones before he set off his traps on them. They caught him up on galactic history and politics and he agreed to join them to destroy the evil Empire. Incidentally they ended up founding a base near when Rusty had dug himself in. They called it Yavin IV.
Now with the Alliance, Rusty mostly works as a hanger mechanic and helps the resource strapped organization salvage damaged droids and ships.

Quest: Vengeance
Rusty spent many years plotting his revenge against the forces that killed his master. He will do all he can to bring the Empire down. He especially has it out for storm troopers, as they remind him of the treacherous clones.

Resource Acquisition: 0 pts
Rusty loves finding junk and fixing it up. Nothing is garbage. It can all be re-purposed.
Rusty is a bit of a hoarder.

Rusty lives up to his name. He is a beat up, well worn R4 unit. Add to that all of his make shift modifications, he looks like a piece of junk. But the R4 series were known for their resilience, and he lives up to that as well. Because of their reliability R4's are a popular unit, found every where. So Rusty easily blends into the crowd on outer rim planets.
Rusty has gone a long time with a memory wipe. Due to his serving under a Jedi Master the Alliance refrained from wiping him, out of respect for the Jedi's memory the droid carries with him. Because of this and because of being alone for years Rusty has become....a little eccentric. It also doesn't help that he still talks like a nerf herder.
Also, due to his long time planet side and his cumbersome frame (he doesn't fit in the Astromech port like he used to) he has developed a dislike of space travel. He'll do it, but he'll let everyone know how he feels.