Advanced Recon Commando: Null-class

Numbering only six, the Null-class Advanced Recon Commandos were the first clones of Jango Fett created by the Kaminoan cloners, and the prototypes for the Grand Army of the Republic. They were deemed a failure by the Kaminoans and were not put into mass-production. They were saved from termination by Mandalorian mercenary Kal Skirata who later adopted all of them.

All of the Nulls were named after Mandalorian warriors.

History
Kal volunteered to train them as "black ops" commandos, named them, and taught them their Mandalorian heritage—sequestered from the other clones throughout their training. Even before two years of age, Ordo and his Null brothers had already undergone flash instructions and live ordnance tests, obtaining immeasurably high scores. After completing their accelerated growth they trained in Mandalorian military and survival combat to kill and destroy by any means possible.

They also had special training for essentials of warfare such as assassination, black ops, anti-terrorism, covert ops, espionage, slicing, and medicine. Kal furthered their training, teaching them how to handle a wide variety of weapons: from blaster rifles to Verpine sniper rifles and hand-to-hand combat. Later in their training, they learned the skills of maneuvering in zero-g.

They received special training that allowed them to act without thinking; they claimed that it resembled the Jedi's use of the Force.

The experience of developing Null ARC troopers contributed much in the production of the Alpha-class Advanced Recon Commandos. During the Clone Wars, the Null-class and Alpha-class ARCs harbored grudges against each other. Whereas the Alpha-class ARCs saw the Nulls as an embarrassment and shame to Jango Fett's legacy of a fully Republic-loyal clone army, the Nulls viewed the Alpha-class ARCs as even more stubborn than Jango and often referred to Alpha-class ARCs as "Alpha Planks," nothing special, ordinary ARC troopers.