Guiron acted as the guard dog of two brain-eating space women, the last of a dead civilization on the planet Terra. The aliens guided him with a mind control device. Guiron proved his combat prowess by effortlessly defeating a Space Gyaos, reflecting its sonic cutter beam and literally slicing it to pieces with his blade. Guiron later fought Gamera, and nearly killed him as well. After a long fight, Gamera eventually managed to defeat the knife headed beast by flipping him upside down - his blade stuck in the earth - then igniting a missile that had gotten stuck in his circular indents, blowing his head off and killing him.
Guiron is an alien monster that normaly walks on all fours, but can also stand on two legs when the situation requires. It is an unusual looking creature, with tough gray skin, a small, sharp-toothed mouth, sleepy-looking eyes and a low, groaning bellow. The most unusual feature of this beast's anatomy, however, is the gigantic blade that it sports on its head, which is nearly as long as its body. On either side of the blade are two openings that hold shruikens. Guiron has a row of small spikes on its back, and seems to have no tail.
Guiron is a cruel savage brute who takes joy in killing his victims, as shown when he proceeds to gleefully mutilate Space Gyaos' corpse, slicing it to pieces while laughing menacingly. However, he is slow and dim-witted, and mostly relies on mental commands from his alien masters.
Guiron is mostly a melee oriented monster. Almost all of his abilities revolve around the massive blade he sports on his forehead. It is strong enough to reflect a blast from a Space Gyaos and cut Gamera's shell. When he can't use his blade Guiron resorts to his secondary attack. A pair of four shurikens stored in two circular indents in the blade. Guiron can guide these shuriken using telepathic waves. They were sharp enough to cut right through Gamera's arms. Guiron can also jump at staggering heights and distances.