The Gods of the Solar Portal are annihilated when one of their own, The god of Darkness, Nihilus Rex, betrays and assassinates their King and Queen. Thrown into exile, the last remaining heir to the Sun, Sol Invictus, grows up believing to be the son of a common Solar Warrior, Dominus Invictus. When he later learns the truth about where he comes from and what his birthright as the Sun Prince is, he reclaims his throne, reunites his people and defeats Nihilus Rex just as their protective dome is destroyed. Dominus sacrifices himself to save the life of his adopted and only son, and as a result, Sol is cast down to Earth in the resulting explosion.
Sol Invictus was brought up to never accept defeat and has been trained to be a ruthless and mighty warrior. He draws most of his powers from the sun's solar rays as well as other radioactive elements to create nuclear fission between his fists. He is immortal as long as there is a sun to sustain power from.
Nihilus Rex, The Countess, Professor Hieronymus Higgins, The Br'kytt Conglomerate
Sol-Army, Protectors of Earth
Sol Invictus along with all of Earth's greatest heroes and villains wake to find themselves imprisoned in an unknown high-tech facility where they are forced to fight to the death against their will. It isn't until the second wave of battles that Sol Invictus is forced to fight where he is pitted against his greatest friend (or the closest ally), Replic-8.
It is at this time that Dragonfly recounts when the duo stood side-by-side against all odds and overcame, saving Earth in the process when all the other heroes fell in battle. He suggests that if either he or Sol Invictus were to kill one another in the Arena, that there would be no hope for the rest of the heroes to detest their situation being that they were so close to one another.
Against all promise, Sol Invictus kills Replic-8 in battle.