Megas was one of king Kaiza's children, along with his Rogles. He was supposed to inhereit the dark world throne from his father Kaiza, but Rogles conspired against him attempting to kill him by using his own army, but Megas survived and repleaced his lost body parts with mechanical parts. Althought he finally returned, Kaiza was revealed to be te one who conspired with Rogles and threw Megas to a dimensional prisson where he remained for long time.
Shortly after Rogles's death, Megas's army raised up again and freed him from his prisson to take revenge from Rogles army and dominate Vecanti, kingdom he claimed by rights. His only obstacle were the Rogles army and the Valis sword wielded by the one warrior who killed his brother, Yuuko Asou. After Yuuko disposed almost all of Rogles's resistance, Megas took his opportunity and killed Valia (MSX2,PC-88/98 and SX68 versions only). Yuuko went to his fortress and beated his henchmen. She finally fought with Megas and sucessed on killing him. While in the PC-88/98 and SX-68 versions he screams about his return as his body vanishes, in the PCECD/TGCD version he agonizes in Yuuko's arms while telling her about why he became the dark overlord he was. Megas finally died on Yuuko's arms.
In the PC-88/98 and SX68 versions of Valis II, Megas was potrayed as a cruel, mercyless and bloodthirst king, even hurting and/or killing his own subbordinated ones. He also intimidates his enemies by telling lies using other events as a false prove.
In the PCECD/TGCD versions of Valis II, Megas is potrayed as a vengeful warrior with a strong determination of recovering what he thinks to own by right even if he has to use force, violence and comit homicide himself to do so. Althought in the end he is seen more like a tragic warrior.
In Valis SD he is like a standard villain, a silly and evil antagonist who dies in a tragicommical form as Yuuko also feels sorry and sad for him.
Megas is, like Rogles, an skilled magician and also a deadly warrior.
Megas can transform his own cape in a dragon-like creature and even create dragon-like projectiles, just like his brother does. Megas also can levitate and create energy bombs. He also wields a saber with enought force to cut anybody in half (as he did with Gillian) and even enough strenght on his arms to pierce anything.
Megas appears as the main antagonist from Valis II in all of Its versions, he is also the main antagonist in Valis SD, the SD parody of Valis II.
Megas appears in the introduction scene of Valis III when describing the events of Valis II. He appears also in Valis IV in one of Yuuko's flashbacks.
Megas makes a cameo appearance in a racing game of Telenet named Dekoboko Densetsu where in the opening scene he appears in the car monitor along with Yuuko.
- Megas seems to be the most bloodthirst from all the main antagonist, having killed many characters in a brutal form (he killed Gillian by cutting him in half and also Valia by piercing her with his own hands).
- Megas's skin and eye color variates deppending on various media: In the PC-88/98 and SX68 versions, his skin is from a jade green color and his eyes are red; in the PCECD/TGCD games and Valis SD, his skin is potrayed as blue and his eyes with a green colour; and in the artworks and Valis X his skin is from a pale green colour and his eyes are white.
- Megas is the first antagonist to have known relatives, his older brother Rogles and his father Kaiza.
- Although Megas has a sword that he uses in the cutscenes, he doesnt use It ingame when Yuuko fights him in the PCECD/TGCD version of Valis II.
- In Valis SD, Megas's monocle is on his left eye instead of his right one as It does in the main series.
- Megas is the only Valis antagonist to have appeared in a game outside the series (Dekoboko Densetsu).
- Megas has the smallest army from the series (in contrast with his brother Rogles), having only his 3 main generals as his only main supporters.
- Megas's seiyuu from the PCECD version (Hirotaka Suzuoki) also voices Zaluga in the same version.
- Megas is the only main antagonist to have died on Yuuko's arms.
- Megas's artwork was featured on the back cover of Valis Visual Collection.