As it seemed no surprise that they would use them as the series began, it can be safely assumed that MechaBeastMen were in use as Galran weapons long before the events depicted in the series. Indeed, their existence may predate Galran and Altean civilization altogether, since flashbacks to Go Lion's legendary battles show the super-robot dispatching creatures much like these. Whatever the case, Galra under Emperor Daibazaal made use of them, though how frequently remains a question. Former Supreme Commander Sadak saw the deployment of one as he hunted for the five space explorers from Earth who became the original Go Lion team as a personal insult. Apparently they were once viewed as weapons of last resort in case an enemy's resistance took an unexpected turn for the worse. Reliance on these creatures may have made Daibazaal more concerned about Go Lion's possible revival, perhaps leading to his original attacks on Altea. The very first MechaBeastMan Go Lion ever faced was even briefly able to keep the super-robot from forming, but as strong as these creatures were, the power of Go Lion kept turning them back, so more and more, Galra's plans called for preventing one of the pilots from being able to join the others and form the super-robot. After the death of team member Shirogane Takashi, Red Lion pilot Kurogane Isamu was forced to knock the attacking MechaBeastMan into a lava pit, which his lion was proof against. A beast based on a 'White Lion' that used the form of Princess Fala's mother was one that used both psychological warfare and binding materials meant to keep the team from forming Go Lion. It was not unknown for MechaBeastMen to have chains, missiles, super-lasers and a myriad of weapons embedded inside their bodies, with many later ones containing some manner of specialized trick meant specifically to disable Go Lion. In one case, a heat wave caused by one of these monsters all but shut down Blue Lion, part of whose power derived from water. In another, a group of suicide attackers threw themselves at Black Lion, creating a thin but immensely strong film over it, keeping it from battle. The weapons and schemes to disrupt formation varied in depth and cleverness, but Go Lion triumphed over one and all.
Not all MechaBeastMen came from Galra's battle arenas, and some are of special note :
A brother and sister from Earth were corrupted by empty promises from Galra, and used against Seido. The brother was turned into a MechaBeastMan and destroyed by Go Lion, after which the sister committed suicide.
When his fortunes reached their ebb, Supreme Commander Sadak was made into a MechaBeastMan. He fared no better against Go Lion than he had as a field commander, and was destroyed.
Crown Prince Samson of Heracles actually volunteered to undergo the process, but the Galrans betrayed and killed him after he failed to defeat Go Lion. His father, King Heracles, attempted to avenge him, and was also killed in front of his horrified remaining children, Princess Amue and Prince Alor.
A female creature with a Medusa-like gaze revolted and 'adopted' Suzuishi to replace her own lost child. She was killed by Galran forces.
A hotshot ace pilot for the Galrans was one of a few who piloted a MechaBeastMan as a craft. His speed alone made him a challenge to Go Lion, but team training overcame it. He was arrogant and demanding, and few among Galra's rank and file were sad to see him fall.
A virus corrupted the earth-moving machines that the team had created to build a children's soccer (football) field, and the machines merged to form a monster. The five lions later replaced the machines and completed the field.
Kogane faced down and partially disabled a MechaBeastMan that interrupted his battle with Sincline, or what turned out to be an enhanced clone of Sincline, revealed in part by way of the monster killing the defiant clone.
Overthrown by his son Sincline, Emperor Daibazaal piloted a MechaBeastMan made in his own image and carefully attuned to his thoughts and wishes. It was also the last and most powerful of all the monsters. If Daibazaal beat Go Lion using it, Sincline agreed to relinquish his father's throne back. A combination of Sincline's further betrayal and Go Lion receiving mystic aid in reforming its broken sword ended both Daibazaal and the MechaBeastMen for all time.
The MechaBeastMen appeared to be of an entirely different species than other Galran soldiers, who were ruthless all by themselves. Both had the rather repulsive habit of dining on meat made from the helpless slaves they bullied and killed. Whether this was needed for them or done to horrify Galra's enemies is not known. Two types of soldiers appeared in the series. Some looked more like Daibazaal, demonic in appearance, while others looked more Humanoid like Sincline. They were sadistic and vile, and apt to be used as cannon fodder by their rulers.
Edits on Voltron mainly consisted of avoiding shots of impaling and splitting the 'Robot Beasts' or Ro-Beasts as they were called. Most were supposedly completely robotic, and the organic ones, save for Sadak/Yurak, were all said to have somehow survived, usually by going into a coma.