Secondary Mutation

The mutants are known to sometimes develop further abilities and appearances. In some instances, those changes are named Secondary Mutation. That page concerns both the referenced Secondary Mutation, named as it, and other further mutations, including those stated to be Secondary Mutations by fans without editorial or canonical confirmation.
That page is currently in rebuilding.Undoniel (talk) 17:03, March 4, 2016 (UTC)

History

Emma Frost and Beast's hands, after their Secondary Mutations

The Secondary Mutation (or "Second Mutation") is a phenomenon in which an existing mutant undergoes another mutation, gaining additional powers, such as healing, or a change in appearance.

Secondary mutation is noted as the appearance of new powers, or an increase in existing powers.

The phenomenon was quickly a subject of public knowledge, as during the first days of Kitty Pryde as an X-Man, Professor Xavier attended a conference on this topic at Johns Hopkins University in Baltimore.

It was stated by Beast that the secondary mutations usually occurred in the twenties of the subjects, and generally appeared in time of great stress.

It has been shown that secondary mutation could be triggered by more or less natural means, like Beast's mutations coming from his initial experimentation on himself, Elixir's triggered by healing himself (though it was suspected to not be a Secondary Mutation by Dani Moonstar), Quentin Quire's by his overuse of Kick (Drug), or even created, as for Emma Frost's diamond body somehow " "created" " by Cassandra Nova.

There is some beliefs and hinting points that the Secondary Mutation are linked to the mutants population state: Beast stated that his feline form was possibly linked to that year's mutant baby boom.

Confirmed and suspected Secondary Mutation subjects

As far as we know the first Secondary Mutation witnessed and stated as such is Emma Frost's diamond body, " "created" " somehow by Cassandra Nova.

After the Stepford Cuckoos demonstrated the ability of flight, they were diagnosed as having a Secondary Mutation by Kitty Pryde and Beast, but regarding to the following events and the revelation of them Cuckoos' origin, that statement can be strongly contested as being in fact the doing of Phoenix.

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Character	Powers Change(s)	First Appearance(s)	First Mention(s)
Beast	Feline form	New X-Men #114	Marvel Fact Files #13
Emma Frost	Organic Diamond Form	New X-Men #116	New X-Men #116
Elixir	Dichromatimorphic Skin (Gold skin)	New Mutants (Vol. 2) #12	New Mutants (Vol. 2) #12 (Controversial to Dani Moonstar)
Husk	Personality swings and omnimorph powers related	X-Men: Regenesis #1 Wolverine & the X-Men #1	Wolverine & the X-Men #41
Iceman	Organic Ice Form	Uncanny X-Men #415	Uncanny X-Men #415
Masque	Biological Manipulation		Uncanny X-Men #487
Stepford Cuckoos	Flight	X-Men Phoenix Warsong #1	X-Men Phoenix Warsong #1; Controversial (Phoenix)
Black Tom Cassidy	Plant-form	Uncanny X-Men #411	Uncanny X-Men #412 Uncanny X-Men #415
Kid Omega	Corporeal Disembodied Psychic Consciousness	New X-Men #138 X-Men Phoenix Endsong #1	New X-Men #138

(List of mutant confirmed to have undergo a Secondary Mutation)

 Mutant powers can continue to mutate, given enough time. 

—Damian Tryp about himself

Engineered Secondary Mutations

After the Incursions wherein the Marvel Multiverse had been decimated then rebuilt.

Refugees from other, now nonexistent worlds had migrated into the Prime Marvel Universe as a result. Some in particular would be Jimmy Hudson who'd still carried the mutation engineering drug known as Mothervine within his very D.N.A.

He along with his fellow cross-dimensional mutants were eventually captured and experimented on by Miss Sinister. integrating them into her New Marauders as she studied this genetic anomaly within her prize.

With backing by Emma Frost and her Hellfire Club affiliates, Claudine had surmised while it initially had the power to engineer spontaneous genetic alteration within the fetal stages birthing new mutants with trigger activated abilities.

It was also discovered, through rigorous and unethical experimentation to have the capacity of triggering secondary and tertiary mutations within fully developed mutants. Though many of these alterations would prove either fatal or derogatory to some of it's test subjects. Those of whom the mothervine effects eventually begin to lose control over their powers and eventually dissipate, or the gene therapy itself proved lethally toxic to the recipient.

A great many enforcers of New Tian having undergone the process of which, gaining vast augmentations to their existing powers. With further testing, Havok deemed it ready for World Wide deployment on the morrow.

Fan-stated and unreferenced Secondary Mutation subjects

Many occasions of further mutations have been shown, without the statements of Secondary Mutations.

The "first known subject" is Polaris. Beast "is actually the second" and it is he who named the phenomenon. (Actually Beast "had his first (unnamed this way) secondary mutation years before").

If you have a reference for one of those mutants, feel free to add it and make the changes.

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Character	Powers Change(s)	First Appearance(s)	First Mention(s) / Note(s)
Beast	Blue-furred ape form; New, more feline form	Amazing Adventures (Vol. 2) #11 All-New X-Men #5
Polaris	Negative emotions absorption, Strength, Invulnerability, Amazonian size	Uncanny X-Men #254

Notes

• The Secondary mutations concept has been very criticized by some fans.
• As an extension of that fact, the concept is often used as jokes by mutants, and even by mutates like Spider-Man.
• When affronting heavily mutated Rastus, Callisto thought of him as a mutant who would had underwent "some kind of secondary hyper-mutation as a response to the Sentinel attack" on Genosha.
• It is unknown as far if mutates can undergo Secondary mutation in that strict definition, but Inhumans have been known to undergo Secondary Terrigenesis.
• In Earth-101001, the Damon-Hall Syndrome is a mutant gene virus that makes mutants get stuck in the secondary mutation form, and become irrational mutant monsters. A serum/drug developed by Hank McCoy can cure and immunize mutants against the condition.