Actarus is the prince of the planet Euphor, also known as Fleed, and the pilot of the giant super robot Grendizer. After the Vegan empire devastated his home world and massacred his family, he escaped with Grendizer and sought refuge on Earth. To conceal his alien identity, he was taken in by the scientist Professor Procyon, who gave him the Earth name Actarus and passed him off as a son returning from abroad. He works as a quiet, unassuming stable hand at the White Birch Ranch. Haunted by the destruction of his planet and the loss of his family, Actarus is deeply melancholic and pacifistic, a calm and thoughtful young man who carries the weight of being the sole survivor of his people. He harbors a profound hatred for war and only fights when absolutely necessary, driven by a desire to prevent Earth from suffering the same fate as his own world. He possesses superhuman strength, speed, and agility, as well as a telepathic ability that allows him to see through solid matter. A notable physical limitation is a severe injury to his right arm, sustained during Euphor’s destruction and contaminated by Vegatron rays, which causes him pain near proton-based weapons. He can instantly transform from his civilian clothes into his pilot uniform. Despite his reluctance, he becomes Earth’s primary defender against the Vegan forces. Over time, he forms bonds with his Earth companions, which gradually temper his sadness. After ultimately defeating King Vega and the Vegan mothership, he bids farewell to Earth and returns to Fleed to help rebuild his home world.