Bly was one of the many clones made from DNA of the mercenary named Jango Fett. He was bred in a cloning facility on Kamino as CC-5052 and was among the first generation of Clone Marshal Commanders. During his training he received the designation "Bly". Bly was trained as an Advanced Recon Commando and his job was to act as an intermediary between the Jedi Generals and the regular Clone Troopers.
Mayor Story Arcs
When the Clone Wars erupted, Bly was put in command of the 327th Star Corps, whom was attached to the Jedi-Knight Aayla. Bly was a trusted ally, but he was bred to be loyal to the Republic above all other things. During the wars, Bly fought on Aayla's side numerous times, but betrayed and murdered her on planet Felucia after receiving Order 66 from Emperor Palpatine. Most likely this was not because of his own will, but simply because Order 66 was made to override any other thoughts or orders. Bly continued to work for the Republic, now known as the Empire and hunted down fugitives. What happened to Bly after that remains to be seen.
Clone Commander Bly plays a mayor role in the "Star Wars: The Clone Wars" cartoon television series.
He has also recently gotten his own action figure.