IN X-MEN: Apocalypse, audiences are about to experience their favorite mutants going up against a villain that is the only one that may rival - or surpass - fan-favorite X-villain Magneto in both power level and popularity.

With hundreds of villains to challenge them in their over 50 years of existence and thousands of comic book issues, how and why has Apocalypse stood out and towered above almost all the rest?

Writer Louise Simonson, who co-created him with artist Jackson Guice back in 1986 (X-Factor No. 6 is the villain's sought-after first appearance), feels she has some answers.

"Apocalypse is the first mutant - a brilliant shape-shifter who is virtually immortal - and sees himself as the father of mutantkind," Simonson said in a recent interview. "In his early years, which I covered in the X-Factor Forever miniseries . . . Apocalypse encountered the Celestials and realized there was a time when humanity might be judged unworthy and destroyed.

"Consequently, he's been using Darwinian principles - survival of the fittest - to kill off the weak and force the survivors to grow stronger, to push humanity to get better and more powerful. He considers himself the Apocalypse of modern man and the father of what humanity will come next - Mutantkind.

"Where Magneto sees mutants as the next step of evolution and strives to protect all mutants, Apocalypse believes in absolute survival of the fittest - so if the Hulk, for example, is stronger than [the X-Men's] Colossus . . . well, in Apocalypse's world he would say, 'Bye, bye, comrade.'

"When X-Factor was created, it caused a split in the "Mutant World" [and] several seminal characters were pulled out of [writer] Chris Claremont's X-Men." However, what X-Factor really needed to cut through the clutter, Simonson said, was a big, bad villain. So she came up with Apocalypse.

"It was due to me, mostly," she said. "I didn't draw it. Jackson Guice did and the visuals in comics are so very, very important.

"Jackson did a great design, though he later forgot he'd designed the character and thought Walter [Simonson, Louise's husband] had."

Louise Simonson said that feeling is understandable since Guice only drew Apocalypse for a few panels and that Walter Simonson's look is the one people most identify with the character.

"Walter and I were amused", Simonson said. "We reminded [Guice] so he'd get some creator money for the toys and such. Walter made Apocalypse so very powerful, that it's hard for people to believe he didn't actually design him. Apocalypse just looked so impressive! [But] Walter did design his ship."

In the end, Simonson feels she succeeded in creating a threat to more than just the X-Men.

"Actually, Apocalypse is a threat to all humanity, though he sees himself as their savior," she said. "He just happens to be a mutant, and he wants everyone else to be one too. So generous of him!"

So how does Simonson feel about co-creating a villain whose name is in the title of a major tentpole movie? "It's always cool, seeing characters you created on the big screen, so I'm excited but slightly nervous. Remember the Steel movie," she asked with a laugh (Simonson cocreated Steel for DC). "I'm hoping for a good script and exciting visuals."