Space Giants (1966-67)

aka’s: Magma Taishi/Ambassador Magma/Monsters From Space/
The Magma/Captain Magma/
Monsters From Outer Space/
マグマ大使

Features an evil mastermind from outer space named Rodak, who plans to take over Earth. Luckily for us, we have the Space Giants – Goldar, Silvar and Gamma – to protect us. The Space Giants live in a cave with an old man named Methuselah and fly around battling the agents of Rodak, who dissolve into a really creepy green sludge when shot.
(In Japanese language, Uncut).

Sold as a 13-DVD-R set