Secondary mutation

In the Marvel Universe, Secondary Mutation was a fictional worldwide phenomenon among mutants that seemed inexplicable, with many previously established mutant characters suddenly developing new or vastly expanded powers. Henry McCoy hypothesized that, since the mutant population was entering the millions at that time, mutant physiology was responding to the need for survival. Thus in rare occasions a mutant's powers change or become even greater, and in rare cases they can develop a new, often unrelated ability. However, the criteria for secondary mutation is ill-defined at best, leaving many fans confused as to their favourite character's status or powers. This use of secondary mutations can sometimes be misused as a Deus ex machina; if the writer can't think of a way for a character to get out of a situation, they can simply develop a spontaneous new power to handle the problem.

Known mutants with secondary mutations

*Polaris (Lorna Dane): after having her mutant powers leeched by her supposed-sister, Zaladane, Lorna developed the first recorded case. Her body mass had increased, along with her strength and resistance to injury. When her secondary powers were used, it developed negative emotions in anyone around her. Later, Lorna regained her original powers after Zaladane's death, and her secondary mutation vanished. This was retconned to be the first known secondary mutation when the concept was first introduced.

*Beast (Hank McCoy): after being seriously injured by the villain Vargas, Sage attempted to use her ability to "jump start" mutation to save his life. This resulted in Beast de-evolving from his simian form into a giant feline form.

*Emma Frost: Emma's secondary mutation activated in the midst of the bombing of Genosha by Cassandra Nova's wild Mega-Sentinels. She transformed into an indestructible organic diamond form that saved her life, but negates her telepathy so she cannot use both powers at once. Recent revelations suggested that it may have been Nova who helped produce the secondary mutation. It was later explained that Cassandra Nova implanted a suggestion in Emma's mind in an attempt to eventually make an escape from the Shi'ar alien protoplasmic Stuff during the same procedure.

*Angel (Warren Worthington III): discovered his new power while being wounded in a battle with a group of werewolf-like mutants called the Dominant Species. Both he and his teammate Husk were severely wounded. Husk almost died, but was brought back through contact with Warren's blood seeping in through wounds on her own body. His blood gained a healing property that can be used to mend and regenerate others. This activation was then retconned as having occurred earlier, in a battle against Black Tom Cassidy, when his skin turned from blue to normal (later described as a result of his healing factor activating). Angel had previously been modified by Apocalypse; whether this included genetic alterations has never been clarified.

*Iceman (Bobby Drake): his supposed secondary mutation was greatly increasing his ice manipulation abilities, but leaving him trapped in his organic ice form and unable to transform back to flesh and blood. However, after the events of M-Day, where over 90% of the world's mutant population became depowered, Bobby is once more able to revert back and forth. This leaves the question of whether his transformation was a second mutation or just an increase in his power he had to overcome.

*Phoenix (Jean Grey-Summers): After the storyline The Twelve, Jean Grey somehow managed to transfer her telekinetic powers to Psylocke, who also managed to transfer her telepathy to Jean Grey. For a time, Jean only had telepathic powers. However, when the NEW X-MEN series stared, Jean's telekinetic powers had returned. Beast implied that it was the result of a secondary mutation for Jean. However, this appears to be retcon later, as it is revealed that as some unspecific point, Jean merged again with the Phoenix Force and that perhaps the Phoenix had given her back her telekinesis.

*Elixir, (Josh Foley): Initially, when Josh's healing powers manifest, he looked like a normal teenage boy. However, after being brutally attacked by Wolfsbane, Elixir was forced to heal himself. The result of which, caused Josh's body to undergo a second, this time physical, mutation, turning his skin from flesh tone to gold. Later, Josh's powers undergo another change, with the revelation of his death touch, which also turns his skin black.