[PRangerX]

Its fun to come up with out own fanon for stuff like this. One idea I have is for the Negaverse to have once been a universe much like ours. Queen Materia wanted power and became so powerful that she became a powerful entity. Her body was destroyed by rebels but it was too late as her essence was strong enough to absorb her universe with her becoming the Negaforce. The Negaverse was born. With all her folllwere evovlimg into Youma. She recruited Shitennou from the other universes she conquered, who retained human like physical forms. And one was chosen to lead as King and Queen. Which others have suggested as well.