Crimos were a type of specialist soldier used by the Federation. "Crimo" is stated by Blake to be a portmanteau of "criminal psychopath". Their chief onscreen role was to assist Travis in his gambit in the Communications Tower on Exbar, in place of his usual crew of Mutoids, who were unavailable to him as a fugitive. It is therefore possible that Crimos were really mercenaries, unable to be enlist in the standard Federation military because of their unstable tendencies.
Crimos displayed a far greater enjoyment of violence than most other Federation soldiers. When Vila asked "why should they want to kill us?", Blake simply replied "because they enjoy it". One Crimo stated that the enjoyment of inflicting pain was the mark of a true Crimo. On Exbar, their leader under Travis, Molok, appeared particularly amused by any instance of pain or fear in his captives. He proudly told Cally of his "high Intelligence Quotient" when she identified him as a Crimo, implying they were considered to be of poor intelligence.
On Exbar, they were seen clad in black armor, bulkier than the standard Federation uniforms, with black skull caps. The Crimos seen on Exbar had armor trims in colours of red, yellow, green and orange, likely signifying different ranks, with green, Molok's colour, being the most senior, and yellow being the most common. They also displayed skill in using unconventional weaponry, which included the use of bear traps and nets to capture the crew of the Liberator, archaic devices rarely seen in the hands of Federation soldiers. On Exbar, only Molok was seen to use a firearm in combat, though a lower ranking Crimo did take Vila prisoner using Vila's own weapon.