If there's one thing the X-Men films have been holding back on, it's exploiting their source material's wealth of villains. Now, based on a cryptic tweet from X-Men: Days of Future Past director Bryan Singer, it looks like the most imposing bad guy in X-Men history will finally make the leap to the silver screen. 2016 will possibly see X-Men: Apocalypse storming into movie theaters.

When you have a villain who is big enough to warrant his name in the title, there have to be a lot of stories worthy of a film adaptation. Here are five classic X-Men stories featuring the Darwinist mutant known as Apocalypse.

"Judgment Day"



Apocalypse made a big splash early on in this three-part epic from the pages of X-Factor. Every weapon in En Sabah Nur's arsenal is on display here, from his giant Celestial starship to his super-powered Four Horsemen. This storyline also sees Apocalypse transform the fallen Angel into the razor-winged Horseman of Death, rechristened as Archangel. While Ben Foster, who played Warren Worthington III in 2006's X-Men: The Last Stand, isn't reprising his role in 2014's X-Men family reunion, Days of Future Past, he could always come back in this film. If not, Apocalypse could always use his malevolent makeover powers on another mutant – probably Wolverine, given how the Fox films work.

"Endgame"



Let's not forget that there's also an X-Force film in the works from Kick-Ass 2 director Jeff Wadlow. If the time-traveling soldier codenamed Cable is destined to headline that film, it might make sense to dive into his origin story with "Endgame." Here we meet Apocalypse's new minions, the Dark Riders (a.k.a. Cannon Fodder), and learn that the survivalist mutant has infected Cyclops' infant son, Nathan, with an incurable techno-organic virus. To save his son, Cyclops gives Nathan over to a time-traveling ally, who takes him into the future where his disease is halted and he grows up to be Cable. To adapt this storyline accurately, the film needs to fix the Cyclops-was-disintegrated problem; if not, major motion picture Cable doesn't have to be a member of the Summers clan.

"Age of Apocalypse"



If there's one thing from '90s Marvel that’s universally beloved, it's this epic, 36-part crossover event that dominated the X-Men comics for four months in 1995. In this dystopian alternate take on the modern day, we learn just how messed up the world would be if Professor X died before forming the X-Men. Wolverine has one hand, Cyclops has one eye, Beast's a villain and Magneto's a straight-up hero. It's really too early to tell, but it'd be wise to place all your bets on this happening. X-Men: Days of Future Past already has a time-travel component, meaning that if the film ends with James McAvoy's young Xavier biting the dust, "Age of Apocalypse" is a guarantee.

"The Twelve"



In this late '90s crossover, Apocalypse kidnapped the prophesied key 12 mutants (nine of which just so happened to be X-Men – coincidence!) that, when hooked up to a Celestial machine, would grant the mad mutant omnipotence. This story is notable because it contains a much more noble death for Cyclops compared to his lackluster demise in X-Men: The Last Stand. If anything gets adapted from this event, it should be all of the Cyclops-resurrection-y parts.

"The Apocalypse Solution"



If the not-yet-confirmed "X-Men: Apocalypse" introduces us to the villain, then this storyline could form the basis for Wadlow's in-development X-Force film. The first arc of Rick Remender and Jerome Opena's critically acclaimed Uncanny X-Force saw the ragtag team going up against the rejuvenated forces of Apocalypse – new Horsemen, new headquarters, new levels of creepiness. Once inside the compound, X-Force is faced with a decision: should the team kill the resurrected Apocalypse, now a young boy with no memory of the atrocities he's committed? One thing's for sure: Apocalypse's arrival means tough times ahead for the X-Men.