Boss, or known as Clone Commander Bly's first lieutenant, took control over the FCN when Bly died on Kamino and had an extreme anti-CIS sentiment.
Boss was 'born' on Kamino, and he was put under command of Commander Bly and Doctor Nuvo Vindi. He took part in various training exercises and was promoted to Bly's first lieutenant because of his remarkable loyalty to Bly, and not the CIS.
He helped orchestrate the clone rebellion at Kamino, and together with many other clones, they fled to Alderaan, where a base was set up.
Boss hated the CIS for destroying so many transports during the escape, and held a personal grudge against Count Dooku. On Bly's orders, Boss contacted Voe Atell, Prime-Minister of the CIS, who previously stated they wanted peace. Boss accepted the offer of neutrality.
Voe soon came under a lot of fire for her actions, and Boss and some clones managed to save her from death. Boss and Voe hid together in the clone base, until they were assaulted by 'republic' forces. They quickly withdrew all their assets from the planet, and went to Yavin 4. This was in fact a fake attack, orchestrated by the Count Dooku.
When they arrived at Kamino, Boss contacted General Grievous for the delivery of arms and supplies in exchange for neutrality. Boss knew that they were a lot weaker than the CIS, but still kept up with the bluff. Eventually, Grievous tracked them to Yavin 4 and stated a proposal. He and Voe were to surrender and the rest of the base would be spared.
Boss agreed to this, and was arrested. Afterwards, on the malevolence, Dooku appeared. He ordered to destroy all the facilities and kill the clones. Boss was infuriated, but he couldn't do anything. He saw his brothers get shot down and killed. He then told Dooku to stop or else he would release all incriminating evidence to the public.
Dooku, believing this was mere bluff, changed to orders to have all men brainwashed and 'reprogrammed' to CIS standards. Afterwards, Boss was sent to Kamino, to take part in a special experiment under leading of Doctor Nuvo Vindi. He had been transformed in a horrible assassin, which would have done anything if just asked.
He traveled to Mandalore, and there he met up with all the mandalorians. Darth Maul saw that he was no longer a normal person, but rather a robotic monster. Maul couldn't stand such a thing, so he stabbed him right in the chest. Boss thanked him as he was dying, and said that he looked forward to meeting Bly (in heaven). He then died and his body was taken by General Grievous, and put inside his lair in a bactatank.