Clone Master was the title of Kaminoan cloning technologists engineers, and scientists, such as Tef Shabiak for Arkanian Microtechnologies or Sayn Ta on Kamino. However, the name became associated with a group of renegade cloners who attempted a coup against the Galactic Empire with their custom-bred Anti-trooper clones.
Kamino was kept under the watchful eye of Emperor Palpatine in order to ensure that the planet's cloning technology remained under Imperial control.
A small group of Kaminoans, resentful of the Empire's presence, began to grow an army of clone troopers to use in order to fight against their perceived oppressors. These rogue clone troopers were called clone anti-Imperial troopers because they were created to fight against the Empire. They wore Phase I clone trooper armor and were mostly Jet Troopers and Rail ARC Commandos.
The uprising was put down in the Kamino uprising. The conflict pitted these Kamino-grown troops against their own genetic brothers serving the Empire: members of the 501st Legion of stormtroopers, led by the bounty hunter Boba Fett, who had great knowledge of the facility.
The Kaminoan clones were exterminated, with Kamino remaining under Imperial control and the rogue cloning facilities being commandeered for the Empire. The leaders of the Clone Masters attempted to escape but failed. The survivors were put under Imperial rule and carefully watched by the Empire, to prevent any chances or hopes of another uprising from occurring in future.
Although the clone rebellion was soundly defeated, this incident convinced Emperor Palpatine to commission the creation of new clones from different templates and the recruitment of non-clone Humans to fill the ranks of the Stormtrooper Corps.
Timothy Zahn, in his Thrawn Trilogy, cast the Clone Masters as the opponent of the Galactic Republic in the Clone Wars, as several authors of the '90s considered that the cloners and their clones were the "villains."
However, after Attack of the Clones revealed the clones were on the Republic's side, the Clone Masters were retconned into being renegades who did not attack until after the formation of the Empire.