ARC-8157 or "Mist" was an Advanced Recon Commando (ARC) trooper that joined clone group The Broken Source during the Imperial Era. During the Clone Wars he was on rehabilitation for his broken knee-joint. That's where he meet clone trooper ARC-3014. He was not like other clones, he didn't like to fight in near battles. He wanted to sneak behind his enemy like mist and killed them there. That's how he got his name. Mist was very late out on the field and that explains why he joined war first when the Empire was taken over. He didn't reach on Order 66 because it was shut down during the rehabilitation.