The team was first formed after the events of the Fall Of Mutants story arc. When the world sees the X-Men's death broadcasted worldwide, no-one knows about their reincarnation, least of all their fellow teammates: Shadowcat, Marvel Girl (then Phoenix II) , and Nightcrawler. Because of this, they join Meggan and Captain Britain to form Excalibur. Their base of operations was inside Captain Britain's home, a lighthouse.
The first adventure in their own title involved the Warwolves, a group of alien creatures which resemble metallic werewolves. They collect human skins and wear them as disguises. In this adventure, they had come to earth looking for the skin of Phoenix, but in a mix up at the train station Shadowcat was captured. Her phasing powers complicated their plot, but soon enough the rest of Excalibur arrived to help. This event was the beginning of Excalibur.
Excalibur took on a more light-hearted tone then the rest of the X-titles. Some of their other early adventures include run ins with villains from both X-men continuity (like Juggernaut) and also incorporated elements and enemies from Captain Britain's Marvel UK adventures (like Gatecrasher and Saturnyne). One example is a fight that broke out between Captain Britain and Juggernaut. There is also the Crazy Gang, which was temporarily ran by Arcade and his Murderworld. More importantly; after a Cross-Time portal opens Excalibur meets many new enemies such as the Lightning Force, an alternate version of Excalibur from Earth-597. Some early themes of the book revolved around each member having issues with their powers.
The team eventually learns (through Merlyn's manipulations) that Roma, their supposed guardian, set up all the events surrounding their formation. All leading up to Excalibur fighting and defeating Necrom and the Anti-Phoenix.
Beginning with issue #71, the creative team decided to more closely associate Excalibur with the mainstream X-men books. With the team pared down to just Shadowcat, Nightcrawler and Phoenix (the rest of the team indisposed for various reasons), they moved Excalibur's base of operations to Moira's MacTaggart's Muir Island. Excalibur then filled out its ranks with other X-men characters (such as Wolfsbane and Colossus) as well as bringing Captain Britain (as the mad Brittanic) and Meggan back to the fold.
The team eventually disbanded to the winds after the wedding of Brian Braddock and Meggan (mostly to facilitate Colossus, Nightcrawler and Shadowcat's return to the X-men.)
Excalibur was originally created by Alan Davis, Paul Neary, and the renowned X-Men writer Chris Claremont. Alan Davis and Paul Neary won an Eisner award for "Best Comic Book art Team" in 1989 during their Excalibur stint.
Excalibur was formed in Britain, and was composed of British super-heroes Captain Britain and Meggan as well as the X-Men's Marvel Girl, Kitty Pryde, Lockheed, Nightcrawler, and a new character Widget. This team eventually expanded to include Kylun, Feron, Cerise, Pete Wisdom, Douglock, Colossus, Amanda Sefton, Moira Mactaggert, Micromax, Mimic and Wolfsbane.
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The second major incarnation of Excalibur bears no connection to the original team other than its name, and was never actually referred Excalibur save the name of the comic book.
After M-Day, several of the X-Men joined Psylocke in visiting England to see how Captain Britain was faring. Although he was happy to see her, their reunion was cut short by the news that Dazzler was attacked and was presumed dead. Upon arrival the group was able to revive her and quickly learned that she was attacked by a group of original X-Men doppelgangers. They learned that these X-Men were from another dimension, and the evil Charles Xavier's mind had been taken over by that dimension's Shadow King. Psylocke was able to help defeat the Shadow King, and the X-Men doubles are still in custody.
The team was brought back in time by the original Black Night in order to save King Arthur's Camelot. With the assistance of Excalibur, Merlin was able to defeat a pack of dragons that threatened Camelot's existence.
After nearly being beaten by the Wrecking Crew, Juggernaut is feeling less powerful than ever. In an attempt to regain some of his former glory, Juggernaut set out for the Temple of Cyttorak to reclaim the Crimson Gem of Cyttorak, the source of his power as the Juggernaut. The rest of Excalibur followed behind. Closing in on the temple, the team had to deal with their feelings for each other as Cyttorak's power brought out negative emotions between them. This included Nocturne confronting Dazzler about the way she treated the Juggernaut, revealing Nocturne's feelings for the Juggernaut. After battling his inner demons, Juggernaut and the rest of Excalibur returned to England. While this was a momentary victory for Juggernaut, he brought the gem back not yet knowing what he was going to do with it. The Black Night also left the team to try to uncover the secrets of his sword.
Nocturne had a stroke. After weeks of hospitalization and rehabilitation, she still struggled to regain the use of her body and mind. With the team's support, Nocturne found the strength to continue trying to reclaim what she used to take for granted. This experience was hard on the team as such an ailment reminded them of their mortality.
Major Story Arcs
Following the events with Arcade and the Crazy Gang, Excalibur was thrown into Inferno. As Excalibur lay in deep slumber, Rachel Summers has a shocking dream depicting her brother through her psychic link. Suddenly, without a moments hesitation, she pounces out of bed and flies directly out of the Excalibur Lighthouse, leaving a gaping hole in the roof. The other members wake up; startled with the noise. Kitty Pryde, Rachel's roommate, attempts to recover from Rachel's uniform psychic attack as she informs the rest of Excalibur what she suspected. Soon, the team had left the Lighthouse, in search of their fellow teammate.
As Excalibur approached New York City, they realized something was very wrong. The sky had changed colour, with dark shadows crossing the sky. After they reached the City, the team split up. Meggan was caught by N'astirh, and therefore transformed into the Goblin Princess. Rachel on the other hand, after being over thrown by a pack of 'Limbo Demons', is suddenly transformed into some sort of 'Plastic Bride.' She is then captured by the demon Crotus, a lowly creature who has finally caught a break. He takes Rachel to the 'Demon Priest,' where they prepare for their marriage. Nightcrawler is having a bit more luck. He had managed to stay away from the heavy demon attacks, but he instead reflects on his powers. He notices that many objects and places in the city are changing. A great example is the car that grows teeth, and a hunger to go with them. This "Demon Car" attempts to eat a crowd of civilians, and Nightcrawler breaks into a fight. As he finished this battle, he finds more inanimate objects becoming alive. This time, a pack of creepy Mannequins.
Kitty Pryde however is not by herself. She and Captain Britain were together as the local theater came alive! Out of nowhere reels of film were flying about the street, sucking innocents inside, as well as Kitty and Cap. Inside the theater they find a warped reality, with Meggan, the Goblin Princess behind it. Meggan, (possibly subconsciously because of Captain Britain's current behavior) plays with Captain Britain, taunting him. Kitty is rather left alone by Meggan, but is however treated to other horrors. But in this tangible world, Kitty figures out she can control it, and therefore summons Illyana Rasputin's Soulsword! With this she defeats Meggan and saves Captain Britain.
Soon the events of Inferno are finished, and the team return to normal, although they find that their powers are now getting weaker.
The Cross-Time Caper occurred when Widget unexpectedly activated himself and transported the Excalibur team and their train across into an alternate world. It was one in which the magic of the earth was very high, leading to Meggan and Captain Britain's powers returning to full capacity. A young knight, Prince William, sees Shadowcat unconscious and thinks the worst when he sees Lockheed, her pet dragon. When the rest of Excalibur arrives the problem is resolved, but the boy is left with a huge crush on Shadowcat. He therefore asks for her hand. She refuses, but is then taken away and 'transformed' into a real princess. The rest of the team are left on their own, and soon find the prince's real match. After that their train is fixed and they 'jump' on to another world.
Excalibur then finds themselves in a world similar to their own, but with one small difference. The heroes all seem to be insane and run around fighting each other, killing one another in the blink of an eye. When Galactus sees this, he is outraged, and decides it is best if the world is destroyed as it is to silly. The team just get out before the world collapses.
We soon find out about the Bounty hunter Gatecrasher and her band of Mercenaries, Technet. They have been sent to earth to find, and capture Phoenix. Unfortunately, she is not there, (she, along with the rest of Excalibur are travelling through alternate dimensions) and with fear of failing her boss, the Technet stay and wait for the Phoenix.
As we travel to another realm, we see a new situation. The team has been split up, all landing somewhere else. Nightcrawler is on a ship and ends up with a beautiful woman who is by herself. Soon though, space pirates attack the ship and Nightcrawler, thinking that he is helping knocks out the boss. It turns out that she was the heir to the ship after her father died. Nightcrawler is left in a sticky situation, and the rest of the team are not better off!
Soon, once again the team is transported to an alternate dimension, one in which everyone is constantly racing. The world is the race track and the sport is everything. We also see Jamie Braddock and his mysterious, reality warping powers. This leads to a disturbing sequence involving Meggan and Phoenix changing bodies.
After we see Jamie Braddock's powers in the alternate dimension, we also see them in the original. It seems that he is controlling his alternate self in a plot to capture the team. Meggan tries to fight him in the alternate world and transforms into different X-Men. In all the confusion Shadowcat enters a portal leading back home, where she is cut off from the team for a long time.
The others stories we see include a world where Iron Man is Evil, and works for the Shadow King. And another in which Illyana Rasputin's Demon side is shown greatly; in a world where super-humans are hunted and captured. This was committed by a group led by none other than the alternate version of Captain Britain and his sister Psylocke.
The Cross-Time Caper eventually ended when they were given assistance by an overseer who was fed up with all of the cross-time damage they were responsible for.
In this reality the Excalibur team was known as the Lightning Force. This world resulted after the Germans won WWII, therefore the team were Nazi's. One of the members, Shadowcat (who is Jewish), was an enslaved Teammate. As well as this, Captain Britain's counterpart was named Hauptmann Englande, and lead the group or mercenaries.
In this reality the team was known as Calibur. Members were: Cap'n Saxonia, Doctor Strange, Hulk, Iron Fist and Spider-Girl who were seen fighting an alternate Kang the Conqueror during Excalibur's journey across various alternate realities during The Cross-Time Caper Saga. They were also seen being flung across several dying universes when The Chaos Wave (a tidal force of chaotic energies unleashed by a tear in the fabric of time/space that was formed when Earth-616's Scarlet Witch created The House of M reality) tore across The Omniverse, rendering countless worlds asunder. It is unknown whether or not if the members of Calibur survived the disaster.