The galactic beast that fires beams from the multiple protrusions on its shoulders, and lets out the electric beams from the monohorn on its head.
Yuma, who was 7 years old when Monogelos attacked, was camping out at Mt. Shishio with his parents. Unfortunately, his parents became victims of this incident. Yuma miraculously made it through without any injuries thanks to the help of the Giant of Light that fought against Monogelos. However, the existence of the Giant of Light (=Rution) was not confirmed publicly and the conclusion at the time was that Monogelos died due to a sudden change in oxygen levels. Monohorn, the horn that Monogelos expanded in size, still stabs the surface of Mt. Shishio to this day.