IG-666, codename "Devil" was a prototype assassin droid manufactured by the Empire to deal with the Rebel threat. It was a prototype in that it was supposed to be able to mimic the traits of a "flawed" droid - a droid that would act much like a human. This was done to better infiltrate rebel bases, where such droids are commonplace. However, Devil's programming made him turn on the Empire - not because he believed in freedom or some other useless concept, but rather because he felt his skills would be better used for his own gain.
As such, one day, he left the imperial facility he was operating from - leaving a trail of blood behind him. Since then, the ISB and more outspoken imperial authorities have been looking for him, as he would be both a valuable asset if reprogrammed and would be a great threat if he defected to the rebellion.

Expertise, greed.
Devil's "good" programming pushes him to always learn and improve from his mistakes. His "faulty" one pushes him to seek what benefits him most - and in the criminal underworld, that most definitely is money.

Bounty - 15
Wanted by the Empire (more specifically, the ISB, see background).

Uses the same body as the IG-88s. Usually jet black, but changes depending on the circumstances (snowy environment, lush forests, more casual look, etc.)