Warning: Contains spoilers for Captain America #10!!The Marvel Universe is an intricate web of alternate realities, branching timelines, and unfathomable power. When one mystery is solved, another takes its place, and now some of those mysteries seem connected to the doors that select heroes like Captain America, Scarlet Witch, and Hulk have encountered. How (or if) they’re linked to one another remains unknown, but they clearly represent a line to powers greater than even the strongest superheroes.

In Captain America #10 Steve Rogers attempts to persuade a new Change Agent to cross through the Front Door to safety and live under Lyra’s protection. Lyra, otherwise known as Life, uses the Front Door to protect those beings meant to appear and shift the world during times of great upheaval.

Elsewhere in the world, the Scarlet Witch uses the gateway called the “Last Door” to find those in desperate need of help, and Hulk and other gamma-beings use the Green Door to reach (or leave) their afterlife. Marvel’s door system continues to expand, forming into something much larger.

Marvel’s Doors Are Bridges Between Life, Death, and Reality

Captain America #10 by J. Michael Straczynski, Jesús Saíz, Matt Hollingsworth, and Joe Caramagna

The Change Agent whom Steve attempts to recruit is named Seer, who has created her own space meant to mimic the sanctuary offered by the Front Door. Nothing can truly come close to the otherworldly protection it offers, however, as the Front Door theater is life. The Front Door offers Change Agents a home and safety until they’re needed in the world, and wards off even Death himself – as Steve learned firsthand. Despite its power, it appears to have other counterparts in the world, and more could be awaiting discovery.

The Green Door guides Hulk and gamma mutates to the Below-Place, the lowest layer of Marvel’s sprawling multiverse. Just as it lets them in, the Green Door sometimes returns them to life (albeit without their memories). Similarly, Scarlet Witch’s self-made “Last Door” guides those with nowhere else to turn. It appears in the greatest moments of need and guides them to help, sometimes over incredible distances. The Last Door works both ways, too, and recently led Darcy to Quicksilver when Scarlet Witch was in danger. These doors are connected to the world’s most powerful forces, but they’re not invulnerable.

These Magical Doors Could Destroy the Universe

Their Existence Isn’t Widely Known, But They Require Protection

Where there is great power, someone (or something) seeks it. Lyra battles her brother, Death, to protect the Front Door. Wanda built her new life around the Last Door’s magic and is facing the Wizard’s “Angel” and its doomsday prophecies. And the Green Door was already compromised by the One Below All and the Leader. Captain America, Scarlet Witch, and Hulk have found or created the first of possibly many doors that tether Marvel’s most incomprehensible forces to the physical universe, and they provide an easy path to destruction in the wrong hands.