Planet of origin: Zigra
Zigrans are an alien species who had already developed interstellar space travel in the late 1960ies. They are amphibious and may somehow look like a silvery grey armoured swordfish or a goblin shark, with a pointed nose, a row of sharp fins on his back, some pectoral fins and glowing red eyes . They can swim with their fins or stand upright on their hind fins/legs.
A zigran scout came to Earth in the late 20th century with the mission of preparing the planet for an all out invasion. Zigrans had the intention of enslaving the human race and raising them like cattle as he came from a planet where instead of people eating fish, fish eat people. When his saucer was destroyed by the kaiju Gamera, the scout, known as Zigra, came into contact with Earth polluted sea water which mutated him into giant size.
In kaiju form, Zigra's combat style is geared towards brutal melee combat. He is able to fire beams that can paralyse an opponent, and then follow through with vicious slashes with his sharp fins. Zigra can also walk somewhat awkwardly on his tail fins.
He was featured in Gamera vs. Zigra, the sixth Gamera film. Like the alien Viras did two films earlier, Zigra used a pair of human children as hostage in order to force the human race to do his biddings, but Gamera engaged him in battle. Gamera eventually threw him on land where the alien was weaker and used a rock to play his theme song on Zigra's dorsal fins like a xylophone before setting it ablaze with his fire breath.