Mark Millar, the creator of Jupiter's Legacy, was told by Stan Lee to stop writing for Marvel.

Writing Marvel and DC comics, according to Millar, was a "training exercise" for Jupiter's Legacy, a superhero saga that is now available on Netflix.

Writing the biggest characters in comics may be a dream come true, but even Marvel legend Stan Lee doesn't recommend staying around indefinitely. Indeed, he advised Jupiter's Legacy creator Mark Millar to write his own. After several comics and a multimillion-dollar deal with Netflix, the Jupiter's Legacy TV series has arrived to compete with Marvel's on-screen adventures.

Jupiter's Legacy is an eight-part Netflix series based on a comic by Millar and artist Frank Quitely. It includes characters such as the Utopian, Lady Liberty, and Skyfox who put a human spin on archetypal heroes such as Superman, Wonder Woman, and Batman.

Jupiter's Legacy enters an already crowded market. The Marvel Cinematic Universe movies and TV shows, the DCEU and Arrowverse, Venom, The Boys, Watchmen, Invincible, Project Powers, and Thunder Force... the list of superpowered series and sequels goes on and on. Millar considered the crowded market when he created the original comic. "I'd just done Marvel's biggest books, I'd done Kick-Ass, and if I was going to do another superhero storey, it had to be the greatest superhero storey of all time," he recalls.

"I was aware that I would never own Marvel or DC stuff," Millar told me over Zoom from his home in Scotland. From the early days of comic books, when writers and artists were not even credited, to today, when their chapters have spawned multibillion-dollar media franchises, "work for hire" has always been a contentious issue. Recently, writer Ed Brubaker lamented that he had received no compensation for creating Marvel's Winter Soldier, despite the character starring in a Disney Plus TV series.

Millar worked on The Ultimates and Civil War comics, both of which explicitly laid the groundwork for the Marvel Cinematic Universe, but he believes he gained something in return. "After writing Marvel's biggest books, I had an audience I could syphon off," he says, and the success of his own creations like Kick-Ass and Kingsman led to the sale of his Millarworld production company to Netflix for £25 million ($31 million) in 2017.

Millar's work for Marvel and DC turned out to be good practise for creating the world of Jupiter's Legacy. This vast superhero superhistory spanned from 1929 to the far future, encompassing a massive cast of characters from multiple timelines. "I just thought I'd treat everything I'd done up to this point as a training exercise," Millar explains.

Millar was involved in the adaptation of Jupiter's Legacy from the writing stage to the six months of editing that followed filming. Lockdown filming restrictions have reportedly halted The Magic Order, Millar's other Netflix project in development, but Jupiter's Legacy had largely finished filming in Toronto when the coronavirus struck, with the exception of reshoots in January.

Because of the pandemic, Millar could work on the edit from his home in Scotland without having to shave, dress, or fly to Los Angeles. In fact, he was able to screen the work in progress (moving the TV outside due to COVID restrictions) to gauge reactions from family and friends. "The problem is that most of Glasgow has already seen it," he laughs.

Millar considered turning the comic series into a film, but Guardians of the Galaxy director James Gunn pointed out that it would be better suited to a 40-hour TV series. In fact, the first season follows two plot lines: the superheroes in the present day and their origin storey in 1929, as told in flashbacks. That origin storey is laid out quickly in the first few pages of the comic, and if Millar were to make a movie version, he would have cut that plotline before the credits. However, for the television adaptation, showrunner Steven DeKnight suggested expanding the backstory instead.

Millar likens the outcome to Steven Spielberg's Close Encounters of the Third Kind. It's a risky move that may alienate readers who already know where the storey is going, but Millar says he couldn't be happier with the decision – and points out that season 1 only uses elements from the first couple of issues of the comic. "If we make a season 2," he says, "we've got a tonne of stuff we could do."