Later, when Wanda Maximoff, AKA Scarlet Witch, engulfed Earth-616 in a reality warp, Captain Britain and Meggan returned from Otherworld to prevent their home reality’s destruction. Despite being assimilated into the Scarlet Witch’s new “House of M” reality, Captain Britain and Meggan saved Earth with the aid of old allies Psylocke, Peter Wisdom and Rachel Summer, AKA Marvel Girl, former foe Juggernaut, and Nocturne (Talia Wagner of Earth-2182, the daughter of an alternate reality Nightcrawler); however, Meggan seemingly sacrificed herself to seal an interdimensional rift, preventing the warp from destabilizing the multiverse. The Scarlet Witch subsequently reversed her warp, but simultaneously depowered most of Earth’s mutant population. Unaware of the cause, mutants across the globe woke on “M-Day” to find themselves powerless. Few recalled the House of M, and Brian retained only a vague impression, leaving him confused regarding his return to Earth, his wife’s sacrifice, and why he could not return to Otherworld. Peter Wisdom, one of the few remaining British mutants, believed that M-Day left the UK vulnerable and in need of Captain Britain to defend it. Following up their own vague recollections of the House of M, Nocturne, Psylocke, Juggernaut and Excalibur veterans Nightcrawler, Shadowcat and Marvel Girl came to check on Captain Britain.
Meanwhile, the cracks in reality permitted the Shadow King—whose Earth-616 aspect had been imprisoned and then banished by Brian’s siblings Elizabeth and Jamie—to bring his Earth-6141 host, Charles Xavier, to 616 in search of vengeance, accompanied by his minions, perverted versions of the X-Men later dubbed Shadow-X. They initially targeted Roger MacEwan of Fraser’s Bank, perhaps because his employer, was “Courtney Ross” (presumably still her assassin and imitator, Sat-Yr9), the combination of a fellow extradimensional with ties to a Braddock drawing the Shadow King’s interest. The former X-Man Dazzler, tried to help a terrified MacEwan escape Shadow- X, only for both to be slain. News of Alison Blaire, AKA Dazzler’s demise galvanized Brian’s visitors to investigate. Some of the group checked the crime scene, reviving a Dazzler inexplicably hanging on to life, while the others went to MacEwan’s intended destination to question Courtney Ross. While questioning Ross did not help identify Dazzler’s assailants’ identities, it did leave the heroes uncertain whether the true Courtney might have been restored in the wake of M-Day. Shadow-X attacked the gathered heroes, but with Sage’s added assistance the villains were defeated and taken into custody. Wisdom took down the Shadow King’s host body, firing energy blades through his brain, helping Marvel Girl to defeat him on the psychic plane.
Afterwards, Wisdom tried to convince his allies to re-form Excalibur to defend the UK. All but Nocturne declined or ignored the offer, with Nightcrawler, Psylocke, Shadowcat and Marvel Girl returning to America. Old Excalibur enemies Black Air sent the body-stealing Warwolves to eliminate the remaining heroes before Wisdom could win them over. Meanwhile, Captain Britain’s return drew other attention—Bran Bardic, AKA Albion of Earth-70518’s war-torn England, like Brian, had been picked by omniversal guardians Merlyn and Roma to defend his world as one of their cross-dimensional Corps only to be swiftly rejected after choosing empowerment from the Sword of Might, symbolizing the path of violence, rather than the Amulet of Right, the path of reason. Raging at this perceived abandonment, Albion had sworn vengeance against the Corps, eventually finding his way across the multiverse to Earth-616 where he recruited Kelsey Leigh Kirkland, AKA Lionheart (formerly Captain Britain), Brian’s chosen successor as 616’s guardian when he ruled Otherworld. Like Albion, Kelsey had chosen the Sword, only to be embittered when Brian informed her that her choice would forever estrange her from her children. As the Warwolves attacked Wisdom, Dazzler, Sage, Nocturne and Juggernaut, simultaneously Albion and Lionheart battled Captain Britain. The Warwolves were swiftly captured and the renegade Corps members retreated before Brian’s allies interfered. In the wake of these attacks, the group acknowledged the need to reassemble Excalibur, moving into a base provided by MI-13 at Empress Matilda Docks.
Subsequently, Black Air equipped Juggernaut’s former criminal partner and depowered mutant Black Tom Cassidy with new technological powers. He assailed most of Excalibur with mechanical vines while they were rescuing survivors of a terrorist bombing at Shepherd’s Cross Railway Station, set by Squadron Leader Colin Hardy of the Scarlet Knights. Meanwhile, across town, Tom and his Black Air allies hijacked the transport moving Shadow-X from Wormwood Scrubs Prison to the more secure Crossmoor facility. Tom slew Dazzler, but she again mysteriously revived, and despite the diversion, Excalibur disrupted the jailbreak. Black Air escaped with Shadow-X but left behind the Shadow King, while Juggernaut convinced Tom to surrender. Transferred to Crossmoor, the Shadow Xavier soon demanded to see Psylocke. When she visited his cell accompanied by Excalibur, the Shadow King revealed he was in control of Xavier and then telepathically took over Excalibur, intending to make Psylocke watch them slay Brian. In response, Psylocke telekinetically induced a stroke in Xavier, but before she could slay him, she was snatched out of reality, recruited into the extradimensional Exiles, Nocturne’s previous group.
Wisdom later visited the hospitalized Jonothan Starsmore, AKA Chamber, whose sudden “M-Day” depowering had caused him catastrophic injuries. Wisdom told Chamber that Excalibur was working on ways to heal him, adding that he hoped Chamber would join them once he recovered; however, ancient mutant Apocalypse’s follower Ozymandias of Clan Akkaba restored Chamber for his own reasons. Chamber subsequently rejected both Clan Akkaba and Excalibur, preferring to find his own path. Brian sought to recruit the Black Knight into Excalibur, but Dane was temporarily possessed by his ancestor Percy of Scandia’s ghost who informed Excalibur that Camelot had been prematurely destroyed by dragons. The Lady in the Lake’s magic sent Excalibur back in time, where alongside Merlin and King Arthur they defeated the dragons, actually Makluan aliens, preserving their own timeline (and diverging the one where Camelot was destroyed into Earth-6120). Back in the present, Cyttorak, the mystic entity who empowered Juggernaut, had grown displeased with Cain’s forsaking destruction to become a hero. Cyttorak telepathically played on Cain’s doubts over reforming, tempting him to return to his Korean temple to restore Cain’s recently reduced powers by claiming the Ruby within. Excalibur and the Black Knight followed, finding Cain moments after he had defeated a new Juggernaut chosen by Cyttorak to replace him; however, Cain resisted returning to Cyttorak’s service. Learning from Cyttorak that Cain had murdered the previous Juggernaut (Jin Taiko) and an entire innocent village to gain his powers years ago, Excalibur considered expelling him upon their return home, but Wisdom, no stranger to a dark past, overruled them, unaware that Cain had taken Cyttorak’s Ruby from the temple. Meanwhile, the Black Knight declined Excalibur membership, setting off on a quest to find his stolen Ebony Blade. Shortly after this, Excalibur helped repel an invasion of extradimensional Martians from Earth-691.
While foiling a bank robbery, Dazzler was again killed then spontaneously revived, but before the team could fully investigate this phenomenon, Nocturne suffered a stroke; her teammates subsequently helped her begin the slow process of recovery. Concurrently, Albion and Lionheart had forged an uneasy alliance with Black Air and Shadow-X, and were recruiting depowered mutants into the Shadow Captains, Albion’s version of the Corps. Learning of this, Sage infiltrated Albion’s group using the persona of Diana Fox, aka Britannia. Lionheart and Shadow-X broke into Crossmoor to free the Shadow King, but when Shadow-X offered Lionheart to their master as a new host, Lionheart slew the Shadow King, then escaped as Excalibur arrived to capture Shadow-X. Using the Crossmoor incursion as a diversion, Albion led his Shadow Captains in a raid to steal a mystic staff capable of disrupting all advanced technology within Great Britain. The undercover Sage tried to prevent Albion activating it, but Lionheart intervened, and a magical backlash from the artifact temporarily extinguished Sage’s true personality, leaving her a loyal follower of Albion. Shadow-X and Excalibur joined forces to stop him, eventually succeeding at the cost of Shadow-X’s lives. During the final battle, Sage overcame the Britannia persona and Lionheart switched sides, realizing that Albion was wrong and that she could not betray her children, her country or its people. Captured, Albion was sent to Crossmoor, while Lionheart was given a second chance, remanded into Excalibur’s custody and reunited with her children.
Learning that the Hulk was attacking the X-Men in pursuit of his step-brother Charles Xavier, Cain invoked Cyttorak, promising to do whatever was asked of him if first Cyttorak could restore him to full power and swiftly transport him to face the Hulk; however, Cyttorak only did the latter, and Cain was swiftly defeated. Realizing that to have a chance he had to give in to his desire for destruction, Cain finally gave in and accepted that he was Cyttorak’s avatar. Restored to full power, he returned to the fight, proving a match for the Hulk until his opponent tricked him into running into a lake. By the time Juggernaut emerged, the Hulk had left. Rebuffing his step-brother’s gratitude, Cain left for parts unknown, warning Xavier that no one should come looking for him as they wouldn’t like what they found.
Merlyn, apparently angry at his successors Roma and Captain Britain, sent the killer Rouge-Mort and her Janissaries to Earth-616 to slay Brian and encouraged the reality-warping Sir James Jaspers, an old foe of Brian’s recently resurrected during the House of M, to attack Roma’s Starlight Citadel. Jaspers, unknowingly infected with the essence of the Fury—the unstoppable killing machine that had previously slain him—transformed many of the defending Corps into pseudo-Fury’s, decimating their numbers.
On Earth-616, Excalibur were still celebrating their victory over Albion and an unexpected but welcome reunion with Brian’s sister Psylocke and Nocturne’s former lover John Proudstar, AKA Thunderbird, both members of the Exiles, when Rouge-Mort attacked. Though swiftly driven off, Rouge-Mort gravely wounded Brian, who was rushed to the Exiles’ extradimensional base for medical treatment. To her surprise, Dazzler discovered her long-missing husband Longshot among the Exiles, rendered amnesiac by their old foe Mojo, leading her to wonder if Mojo was also responsible for her recent apparent immortality. Learning of Jaspers’ assault on Roma, the two teams rushed to her aid, with Wisdom and Psylocke recruiting Albion from Crossmoor to replace the injured Brian. Roma transferred her memories to Sage moments before Merlyn apparently slew her. Battling Albion, Jaspers transformed into the Fury, but with the timely assistance of a recovered Brian and the Exile Blink, the Fury was seemingly destroyed. His allies defeated, Merlyn fled, but not before he was apparently infected by the Fury’s remains. Having regained some of his memories during the conflict, Longshot elected to return to Earth-616 with Dazzler, while Sage, struggling to cope with Roma’s memories, chose to stay with the Exiles. With Longshot and Dazzler’s return to the United States, Excalibur apparently subsequently disbanded under undisclosed circumstances.