Monsters used by members of Planet Doom and the Drule Empire were often send to fight the two Voltrons of the Galaxy Alliance. The Robeasts from planet Doom, reared in gladiatorial combat, are humanoid monsters created through a combination of superscience and Haggar's magic, usually from prisoners of war though some of them are simply giant robots piloted by Doom soldiers. The Drule Robeasts that battled the Explorer were uniformly technology based. In Voltron Force, a new series of Robeasts are produced by infusing Apex predators from various planets with Haggarium. The resulting creatures are biomechanical beasts with the Haggarium enabling them to normally weaken Voltron with special abilities augmenting their natural talents.