While the X-Men may have found the solution to the ongoing eradication of mutants thanks to the new Krakoan resurrection protocols, Marvel's mutants still spent decades dealing with character deaths that shocked and devastated fans.

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Although characters like Magneto appeared to die frequently, and other mutants like the Muir Island X-Men were revealed to have died in the past in later series like 2005's X-Men: Deadly Genesis, these following characters were the first to be killed off in the pages of the comics, but unfortunately not the last.

10 Bolivar Trask Sacrificed Himself To Stop His Own Creation In Uncanny X-Men #16 (1965)

X-MEN - Bolivar Trask and Master Mold

The Sentinels first appeared in 1965's X-Men #14 by Stan Lee and Jack Kirby alongside their creator Bolivar Trask, who saw mutants as a threat to humanity after he discovered both of his children were mutants.

The mutant-hunting robots rebelled on their creator after the first encounter with the X-Men and attempted to force him to create more Sentinels. However, after he learned that the X-Men were actually mutants fighting for the protection of themselves and humanity, he sacrificed himself in an effort to destroy Master Mold and stop his creations.

9 Kevin Sidney/Changeling Died While Impersonating Professor Xavier In Uncanny X-Men #42 (1968)

X-MEN DEATHS - Changeling from Marvel Comics

While it appeared to the X-Men that it was Professor Charles Xavier who had perished in the pages of Stan Lee and Jack Kirby's X-Men #42 during a battle with the sub-human known as Grotesk that left his students devastated.

However, it was only after the X-Men dealt with an invasion from the alien Z'Nox that they learned Xavier had actually gone into hiding to prepare. The mutant who had died was actually Kevin Sidney/Changeling, Factor Three's mutant shapechanger with terminal cancer that agreed to stand-in for Xavier, which led to his ultimate sacrifice.

8 John Proudstar/Thunderbird Died In A Plane Explosion On A Mission In Uncanny X-Men #95 (1975)

X-MEN - Death of John Proudstar/Thunderbird

The X-Men's first encounter with Krakoa led to most of the team's capture, the death of the aforementioned Muir Island X-Men, and the formation of a new team of international mutants in Len Wein and Dave Cockrum's Giant-Size X-Men #1.

RELATED: X-Men: 5 Reasons Why Warpath Is The Strongest Proudstar (& 5 Why It's Thunderbird)

While the new team was successful in their first mission, they would suffer their first casualty in Uncanny X-Men #95 by Chris Claremont, Wein and Cockrum. John Proudstar/Thunderbird was killed in an aircraft explosion during a battle with Count Nefaria, scarring the team and leading to his brother James' later vengeful debut as Warpath.

7 Jean Grey Sacrificed Herself During The Dark Phoenix Saga In Uncanny X-Men #137 (1980)

Cyclops reacts to Jean Grey's death during the Phoenix Saga

One of the hardest-hitting deaths the X-Men have ever experience occurred during the iconic "Dark Phoenix Saga," when Jean Grey committed suicide on the moon in Uncanny X-Men #137 by Chris Claremont and John Byrne. Following Jean's corruption by the cosmic Phoenix Force, she became the powerful Dark Phoenix and ultimately destroyed an entire alien planet.

When Jean recovered she was put on trial by the Sh'iar, and after fighting a pitched battle she decided to sacrifice herself instead of becoming the Dark Phoenix again. However, it was later revealed that the Jean who died on the moon was actually a construct created by the Phoenix Force while the real Jean healed.

6 Hellfire Club Members Were Killed During Battle With Nimrod In Uncanny X-Men #209 (1986)

X-MEN - Death of the Hellfire Club Members

Harry Leland was the Black Bishop of Sebastian Shaw's Hellfire Club who had the mutant ability to alter the gravity of anyone in his vicinity by increasing their mass, which he used effectively against some of the X-Men's most powerful hitters.

When the powerful Sentinel from the future known as Nimrod interrupted a battle between the Hellfire Club and the X-Men and killed Black Rook Friedrich von Roehm, Leland suffered a heart attack during the battle. He used the last of his energy to increase Shaw's mass as he hurtled towards Nimrod, shattering the Sentinel before he died.

5 The Morlocks Were Decimated By The Marauders In The Mutant Massacre (1986)

The results of the X-Men Mutant Massacre

1986's Mutant Massacre event was a crossover storyline that ran in the pages of Uncanny X-MenX-Factor, New Mutants, Thor, Power Pack, and even Daredevil, featuring the brutal murders of a number of sewer-dwelling mutants known as Morlocks.

Mister Sinister's vicious team of Marauders entered the sewers and began massacring hundreds of mutants. The mutant teams arrived to stop the total execution of the Morlocks, but they suffered a number of serious injuries that included the damage to Angel's wings that would lead to his transformation into Archangel.

4 Doug Ramsey/Cypher Was Shot By The Ani-Mator In New Mutants #60 (1988)

The New Mutants mourning the death of Doug Ramsey

Fans were stunned by the death of Douglas Ramsey/Cypher in Louise Simonson and Bret Blevins' New Mutants #60, which took place during the Fall of the Mutants event that launched the various mutant teams in new directions. The New Mutants were returning their new friend Bird-Brain to the island of the Ani-Mator when they encountered his demented creator.

RELATED: The 10 Most Successful New Mutants To Ever Join The X-Men

Cypher's mutant abilities weren't helpful in battle at the time, but he didn't hesitate to throw himself in front of his teammate Wolfsbane when Ani-Mator attempted to shoot her. Ramsey would eventually return from the dead during the Necrosha event, though his death devastated his team for years.

3 Madelyne Pryor/Goblin Queen Committed Suicide During The Inferno Event In X-Factor #38 (1989)

X-MEN - Death of Madelyne Pryor

Cyclops started a new life after the death of Jean Grey when he met and fell in love with Madelyne Pryor, a woman who was the spitting image of his former lover that was eventually revealed to be a clone of Jean created by Mister Sinister.

Cyclops and Pryor were married with a new baby when Cyclops first learned of Jean Grey's return, and his abandonment of his family led to her eventual demonic corruption and transformation into the Goblin Queen during the Inferno event. Pryor's origins were revealed and she was defeated, leading to her first death in Louise and Walter Simonson's X-Factor #38.

2 Irene Adler/Destiny Was Killed By Legion During The Muir Island Saga In Uncanny X-Men #255 (1989)

Mystique holding an unconscious Destiny in X-Men

Irene Adler often worked against the X-Men as the precognitive mutant Destiny alongside Mystique on teams like the Brotherhood of Evil Mutants and Freedom Force, though they also frequently worked together during large events. When the Shadow King took over the mutants on Muir Island, almost all of the mutant teams got involved, including Destiny and Freedom Force.

While Destiny was killed by a mind-controlled Legion in Chris Claremont and Marc Silverstri's Uncanny X-Men #255, she would continue to play a large role in the future of the X-Men, most recently in Jonathan Hickman's House of X/Powers of X event series that relaunched the X-Men.

1 Warlock Was Killed During The X-Tinction Agenda In New Mutants #95 (1990)

NEW MUTANTS - X-Tinction Agenda

The X-Tinction Agenda event saw a number of young mutants kidnapped by Cameron Hodge and his mutant-hating group The Right to be imprisoned and experimented on the island of Genosha, which included New Mutants members like Wolfsbane and Warlock.

While he was injured during the kidnapping, Warlock still sacrificed the majority of his remaining energy to help free his teammates from their cells, though he ultimately perished after Hodge attempted to steal Warlock's unique alien power.

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