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Art by Ethan Van Sciver
The Source Wall is a fictional structure in the DC Comics Universe. The wall lies on the edge of the known multiverse. Beyond the wall lies what is known as the Source, a cosmic essence or being that is the "source" of all that exists. The wall is theoretically passable. However, all those who have tried have been inevitably trapped in it. Source wall explosion is a multiversal explosion that can destroy infinite dimensions. Unimaginable strength was required for Superman to pull Highfather's staff from the source wall. 
Creation and inspiration
The wall itself was not created or depicted by Jack Kirby, although he did refer to "a final barrier" before the Source and described the imprisoned giants around it. It was first shown in The Uncanny X-Men and The New Teen Titans cross-over and was created by Walt Simonson and Chris Claremont. Simonson provided this account in a post on Comic Book Resources:
"The Source Wall as it is currently understood visually in the DCU first appeared in the X/Titans crossover. ...the Wall as such did not appear in Kirby's New Gods.
What did appear was a four page introductory sequence in New Gods #5 in which Metron, using his Mobius Chair, explores the 'Final Barrier'. 'And somewhere beyond--lies the Source: the greatest of mysteries.' An additional description suggests that this is the Promethian Galaxy--a place of giants--where 'all roads to the Source come to an end--'. Visually, there's a double page shot of a giant strapped to an enormous piece of Kirby debris. There's another panel with a large head of a female who tried to achieve 'the maximum state'. And failed. And, in the text, Metron notes that 'beyond all the knowledge and sweeping concept at our command, the mystery of the Source lies--serene--omnipotent--all-wise.'
There is, however, no shot of a 'Source Wall' as such. No final visual barrier beyond which an entity may not venture. No wall full of entities who tried to breach the final barrier and failed and became subsumed within the Wall.
Chris and I invented that notion--and its visualization--for the X/Titans book, clearly extrapolating from what Jack had done.
The neatest part of the invention is that apparently, the notion of the Wall and its execution were such a perfect fit for the existing New Gods mythology that folks don't really remember exactly where it came from."
According to Jack Kirby at a San Diego Comic-Con appearance in the late 1980s, the inspiration for the size of the Wall comes from "Rock my soul in the bosom of Abraham", a religious song that contains the lyrics, "So high you can't get over it/So low you can't get under it/So wide you can't get around it/You gotta go through the door".
One of the few known persons to have entered the Source was an amalgam of Zeus, Odin, Ares, Jove, and Highfather. Six others are known also to have passed the Source Wall: Superman in DC Line One Million, set several hundred centuries in the future, is implied to have passed through the Source Wall and studied under the Source itself, gaining many abilities; Barry Allen (in Super-Team Family #15); the Spectre (both Jim Corrigan and Hal Jordan); Metron working with Swamp Thing (in Swamp Thing #62); and Lucifer Morningstar. Highfather and Darkseid together have managed to destroy the Source Wall before. The Flash went into the Source for a cure for Orion of the New Gods, but did not remember anything from his time within. The original Spectre, Jim Corrigan, once passed through a crack in the wall and entered the Source during the "Genesis" crossover in Spectre (vol. 3) #58 while searching for God, who was missing from Heaven. During his time within the Source, he was given a brief glimpse of what it was like to be "God" before being forcefully shunted from the Source to continue his quest elsewhere with the vague instructions, "First to Earth, then within." And during the short time that Hal Jordan spent as the Spectre, he also passed beyond the Source Wall and had a conversation with the Old-Timer, formerly one of the Guardians of the Universe, and saw a giant Green Lantern battery. While talking with the Old-Timer, he asked him, "Is this the Source?" The Old-Timer replied, "It is your understanding of it." The Old-Timer then brought Jordan into the battery and explained to him that without any positive or negative charge, there would be no energy or life. After leaving the Source, Jordan felt as though a part of himself was still in the Source. When Lucifer went past the Source Wall, he saw what looked like a huge yellowish man made of rock. Lucifer then stood on its shoulder while looking for Michael in the DC Universe. Whether or not this is what the Source really looks like or is how Lucifer views the Source is left unknown. It seems that humans and other beings, such as angels, when they pass the Source Wall view the Source differently.
In the final confrontation with Gog, the Justice Society defeat the powerful god by removing his head, with Superman and Starman using a portal to take the head to the Source Wall to trap Gog for good.
In Countdown, it is revealed that the 52 universes are each surrounded by a source wall, with the Bleed between the source walls of the various universes. The Monitors refer to an impending disaster if they do not act to stop travel between the 52 universes, and in issue #38 of Countdown, they finally reveal that each time a being passes between universes, they break a little of each universes' source wall. If a source wall is breached too many times, it will collapse and lead to chaos and the destruction of its universe. In Countdown #23, Superman-Prime operates out of a cave within the Source Wall itself, specifically a section bordering Earth-15. He mentions its deterioration and later blasts it with his heat vision, causing a devastating chain-reaction which seemingly obliterated Earth-15.
Darkseid and the Source Wall
Darkseid's connection to the Source Wall is very notable because he has not only been attached to it, but removed from the wall multiple times. In Jeph Loeb's run of Superman/Batman, Darkseid is thrown onto the wall by Superman and later removed from it because of a deal brokered with an alternate version of the villain. Throughout Darkseid's rule of Apokolips and reign as a New God, he has made it one of his primary goals to breach the Source Wall.
Darkseid's father, Yuga Khan, once attempted to unravel the unknowable mystery of the Source as well. However, like so many before him, Khan was made part of the great wall. One of Darkseid's attempts to breach the wall freed Yuga, but his own insatiable hunger for the secrets of the Source returned him to the imprisonment of the Source Wall.
Death of the New Gods
The Death of the New Gods miniseries features the Source Wall extensively, and updates a number of elements in regards to it. In addition to a second Source Wall being created to store the souls of the slain New Gods, the Source itself reveals that it has never truly resided behind the wall, and that only the Bleed rests beyond the wall. The wall is one aspect of the universe that is preventing the Source from merging with its "other half" that was split into the Anti-Life entity after an attack by the Old Gods. It ultimately conspires to destroy the Source Wall, allowing the Anti-Life entity to fully enter our universe and the Source to merge with it, becoming whole once again. At the end of Countdown, a battered Source Wall is shown, with chunks of the wall floating in space.
In Superman/Batman: Torment, Superman is imprisoned within the Source while Desaad controls Highfather's staff. However, Batman is able to take control of the staff, and Superman uses it as an anchor to pull himself through the Source Wall and out of the Source.
In Lights Out, a giant calling himself Relic emerges from what is called ‘the Anomaly’, a point in space/time that does not conform to the normal laws of the general universe, and begins a war against the Lantern Corps of the Emotional spectrum. It is revealed that Relic is a scientist that came from the universe that existed before the current universe. Relic warned the ‘Lightsmiths’ of his universe that the emotional spectrum was a limited resource and could be exhausted. To prove his theory, he searched the universe looking for the ‘reservoir’ of the emotional energy of the universe. His explorations brought him to the Source Wall of his universe. When the various emotional energy collectors went dark and the emotional spectrum was exhausted, his universe began to collapse. Relic entered the Source Wall as a last act of discovery as his universe died. As he entered the wall through a rift, he was broken apart at a molecular level, and passes through to be born in the current universe. Green Lantern (Vol 5) #21 (September 2013).
At the conclusion of Lights Out, it is revealed that the `reservoir´ of the emotional energy is located behind the Source Wall which Kyle Rayner, as the only White Lantern and possessed by multiple dying Entities is able to pass through and temporarily recharge both the `reservoir´ and the Source by delivering the entities there, thereby postponing the death of the universe. He has no conscious memories of what happened inside the Source Wall; however, a Guardian of the Universe read his mind and indicated that the knowledge is present, just suppressed.
Eventually it was discovered that hidden behind the Source Wall was also the Anti-Life's opposite member, the Life Equation, which Kyle Rayner had unknowingly claimed and supplanted within his White Ring, to escape the Source Wall after he replenished the Emotional Reservoir.
During the Godhead storyline, Hal Jordan is forced to make an uneasy alliance with Black Hand against the New Gods of New Genesis. In the battle that occurs near the Source Wall, Black Hand unleashes the spirits of the fallen Green Lanterns against the New Genesis soldiers but when the New Genesis soldiers surrounded them, he smirks to see the Source Wall was a mass grave. Black Hand reanimates the grave of the Source Wall to attack the New Genesis soldiers, however touching the Source Wall was not without consequences for Black Hand as his arms began to turn to stone. He soon discover that he no longer could raise the dead and instead everything he touched would become stone. Hal would return to the Source Wall with an unconscious Black Hand and asked Relic, who had been studying the Source Wall, to find a way to undo Black Hand's power effects. However Black Hand awakes and attacks them, but the Source Wall eventually drags him to it and consumes him. While not seen, its implied that all the reanimated leviathans were also dragged back into the Source Wall.
By the end of Dark Nights: Metal, when Batman, Wonder Woman, Hal Jordan, Aquaman and Superman were forced to use the tenth metal, which has the ability to create or destroy matter based on its wielders' desires, to defeat Barbatos and rebuild the destruction left in his wake, they also inadvertently reached the Source Wall and added sublimated desires into the Universe, breaking the Source Wall wide open. Batman also theorizes that the Source Wall has actually been hiding the DC Universe from whatever exists on the other side- and now that it's open, whatever lies out there (Imperiex and Yuga Khan are hinted at), now have full access to the current Universe. The first threat arriving beyond the Source Wall are the Omega Titans, four ancient cosmic beings, named Entropy, Mystery, Wisdom and Wonder, that were awakened when the Source Wall broke and are believed to have created life in the DC Universe by seeding planets millennia ago and now plan to reabsorb these planets to see which one is the true intelligence of the universe, another side effect of the broken Source Wall is that the Hypertime is dying, furthermore, planet Earth as since began being bombarded with cosmic energies and exotic debris from the Source Wall which are causing random emergent events that dangerously alter and transform some earthling life-forms, humans included. Another threat that came beyond the Source Wall was a sentient sun called "Umbrax", a timeless, dark emotional force of the cosmos connected to and acting as the source of the Invisible Spectrum and the "heart" of the Ultraviolet Corps. As it turns out, beyond the Source Wall exists an energy field known as the Force Barrier, that was concealing and condemning to dormancy six of the Seven Hidden Energies of Creation (the Speed Force and its negative are revealed to be among the forces).. When the Source Wall was breached the Force Barrier was damaged, releasing one of the energies, the Still Force, which broke in the process the seal of Umbrax. Later Hunter Zolomon manipulated Barry Allen and Wally West into running fast enough to finally break the Force Barrier which not only weakened even further the Source Wall but also allowed the Sage and the Strength Forces to be released. The destruction of the Force Barrier also saw the release of the real Bart Allen who claimed to have been held back in the barrier. Barry would later be shown the truth behind the forces which are revealed to be part of the "Forever Force", however, they are all in contention, not cooperation, and because of that were locked away by a user of the Speed Force, otherwise the forces would tear the Multiverse apart.
Source Wall disaster
It is also revealed that the Source Wall served as the prison of Perpetua, the first creator and mother of the Monitor, Anti-Monitor and World Forger. Having designed the previous universe as a dangerous, self-sustaining weapon, Perpetua was betrayed by her sons and locked away behind the Source Wall alongside the seven unnatural and deadly forces she created. The Omega Titans are actually Perpetua's jailers and when the Source Wall was breached, they awakened in order to consume planets for energy to fix the Source Wall, a necessary sacrifice to keep Perpetua locked away. With help from the New Gods, the Green Lantern Corps, the remaining forces of the Thanagarian Empire and the Titans, the Justice League retrieve the remaining three Omega Titans and with Starman channelling the deceased Entropy Titan's power into Hawkgirl, they tried to fix the Source Wall, only for Brainiac and the Legion of Doom to interfere and free Perpetua, who uses her powers to finally destroy the Source Wall, before it exhausts her and her corporeal form is retrieved by Brainiac. The destruction of the Source Wall causes the end of the Fourth World as New Genesis and Apokolips vanish and the effects of it were felt on various places such as Earth, the Ghost Sector, Heaven and the House of Heroes. All that remains is a burning consuming void that takes its place and Ganthet says the Multiverse will now die within a matter of months. Starman and Martian Manhunter deduce that with the Source Wall's destruction, Perpetua's siblings may arrive to enact punishments on the Justice League for what transpired. Its also established that the hand Krona catched a glimpse of when he pierced the temporal barrier to view the beginnings of time itself, is of Perpetua depositing the speck that would become the entire cosmos.
In other media
- The Source Wall appears in the final episode of Justice League Unlimited, "Destroyer". Metron takes Lex Luthor there to find the Anti-Life Equation. Metron himself is unwilling or unable to take him any further, and warns Luthor that only a "twelfth-level intellect" has a slightest hope of surviving such an experience. Luthor dryly states that he is overqualified then leaps into the wall. He is seemingly correct, as shortly after, he appears again on Earth in possession of the Anti-Life Equation. Dwayne McDuffie when asked what happened to Lex Luthor and Darkseid when they seemingly exploded from the Anti-Life Equation stated that they were fused with the wall, as all living things that solve the equation are. As a subtle homage to Jack Kirby, an image of Galactus can be seen on the wall.
- In the third issue of JLA/Avengers, Doctor Doom is imprisoned in the Source Wall during an assault on the DC Universe, where he was defeated by a Justice League team that included Hawkeye.
- In Young Justice: Outsiders, the Source Wall appears as a battlefield where Superman and Superboy fight off Parademons, while Metron observes from afar.
- Superman/Batman vol. 6: torment (Feb 16 2011)
- Simonson, Walter (November 22, 2006). "The Source Wall". Comic Book Resources.
- Superman/Batman #13 (October 2004)
- Teen Titans (vol. 3) #100 (August 2011)
- Superman/Batman vol. 6: torment (2011)
- Green Lantern Annual #2
- Green Lantern #36
- Green Lantern vol. 5 #37 (December 2014)
- Green Lantern Annual #3
- Green Lantern #42
- Green Lantern #43
- Green Lantern #46
- Dark Nights: Metal #6
- Justice League: No Justice #1
- Justice League: No Justice #4
- The Flash #50
- Titans (2016) #23
- Justice League Annual (Volume 4) #1
- Justice League Vol. 4 Annual #1
- Justice League (2018) #22