IG-84S was an IG-84 assassin droid programmed to be an Imperial war droid. However, he was found dangerous to the Imperials, so they attempted to dismantle him. Before they could, he abandoned his programming and escaped the first death star, the station he was aboard at the time, just before the beginning of the Battle of Yavin. The attacking rebels allowed the IG to escape without any entanglement with the Empire.