Before Primus hid himself away in slumber, Unicron utilized the mental link the two shared to program mental commands into weakminded Transformers. These sleeper agents would activate, assemble, and assassinate the leader of Primus' armies when the time came for Primus and Unicron's reckoning.
They wear Unicron hats.
Marvel Comics continuity
After Primus named Optimus Prime the leader of the army of Cybertron, the sleeper program activated, compelling the Unicron cultists to gather and assassinate him. They attacked Prime when he and Scorponok were discussing their fears of their own mortality. Scorponok realized that they were after Prime, but decided to help anyway. Eventually, the Autobots and Decepticons came to the aid of their leaders, and defeated the cultists. Later, Primus told Optimus that he had deliberately named him leader of the army with the intention of drawing out the cultists. Royally pissed that he had been used as bait by God, the Autobot leader prepared to give Primus a piece of his mind.
Then Unicron arrived...and hell followed close behind him.
IDW Beast Wars comic continuity
Rartorata was recruited from the ranks of these cultists.
- Design elements of the Unicron cultists were based on the Teenage Mutant Ninja Turtles, which was kicking Transformers' butt in the toy aisles at the time. The cultists (sometimes) had two fingers and a thumb on each hand, two toes on each foot, and each carried either a sai-like weapon or a katana. However, their battlecry was "DEATH!", not "Cowabunga." This would not be the only time that hordes of disposable robots in Transformers would have elements based on Teenage Mutant Ninja Turtles.