In the world of Marvel, mutants are defined by their abilities. Each mutant has their special “thing” -- a gift (or curse) that the X-Gene gives them. Some of these abilities are physical ones, like Anole’s scaly skin, and some are mental, like Psylocke’s telepathy. These powers manifest during puberty and, by a mutant’s late teens, are fully developed. Or, at least, they’re supposed to be. In the last few decades, X-Men writers have become fascinated by the idea of secondary mutations. These mutations appear after a mutant’s initial X-Gene manifestation. They frequently elaborate on the powers a mutant already has, but sometimes they can be pretty random. Some secondary mutations are super powerful, and some are just physical changes, but one thing is for certain: they aren’t super common.

Although we’ve seen a recent increase in secondary mutations (mostly thanks to the X-Men Blue series) most mutants still don’t go through a second mutation. Why a mutant may or may not manifest supplementary abilities is somewhat debated, with some readers believing it has to do with latent mutant genetic material that didn’t evolve earlier. This would make sense, since secondary mutations are typically linked to traumatic and stressful events. It’s a little similar to how Deadpool got his mutant power after a horrible, painful experience. There has to be a trigger to get the genetic material going. For most mutants, there’s no such thing as a secondary mutation. But, for the lucky (or not so lucky) few, more power beyond the typical single mutation awaits. CBR is counting down the 20 most powerful secondary mutations in the world of Marvel.

20 ICEMAN: ICE FORM

Iceman Secondary Mutation

Iceman is already one of the most powerful mutants in the world, with an Omega status that rivals classic characters like Magneto and Charles Xavier. You would think his secondary mutation would only make him stronger, but in this case it’s just the opposite. After going through a serious chest injury, Bobby underwent a second mutation.

His entire body became encased in ice -- permanently. Before, he could go back and forth between his ice form and his human form. This allowed him to live a (fairly) normal life. After his secondary mutation, neither Iceman’s powers or morale improved. He became depressed and found that his permanent ice form could be easily smashed.

19 HUSK: PERSONALITY MORPHING

Husk Secondary Mutation

Paige Guthrie, aka Husk, has one of the strangest mutant powers in the Marvel Universe. Before her secondary mutation, Husk was a transitional omni-morph, meaning she could physically tear away her skin in order to reveal a new material underneath. In past comics, she’s morphed her skin into rock, diamond, wood, and glass.

Husk has always had troubles with her powers, such as not being able to morph multiple times without intense pain. However, things started getting much worse in recent series. In Generation X, Paige suffers from dramatic mood swings and patchwork morphs. It’s revealed later that her secondary mutation causes her to change personalities every time she morphs. As you can imagine, that keeps her from using her powers for a while.

18 ELIXIR: SKIN COLOR

Elixir's secondary mutation turning his golden skin black

Elixir is known for his signature golden skin, but he wasn’t always like that. For a while, Elixir only had his mutant healing ability and not the physical aspect of his mutation. It was only after Elixir used his ability to heal himself after a fight with Wolfsbane that his strange skin color appeared.

As is so often with X-Men, Elixir’s secondary mutation is a little more complicated than just a golden hue. Most of the time, Elixir’s skin is golden, but if he uses his Omega-level abilities to hurt someone, his skin turns a metallic shade of black. Prodigy thinks Elixir’s secondary mutation somehow messed with his brain chemistry, causing involuntary changes to his body.

17 WOLVERINE: PRIMAL (DE)EVOLUTION

Wolverine Secondary Mutation

A lot of fans don’t know this, but Wolverine went through a secondary mutation (of sorts). After Magneto used his magnetism powers to rip the adamantium from Wolverine’s skeleton, Logan’s mutant gene went berserk. Since his healing factor no longer had to fight back the poisons from the adamantium, it could focus on putting Wolverine through a secondary mutation. In the months following Magneto’s attack, Logan began evolving, or, to be more specific, devolving.

This version of Logan was considerably powerful since his level of bloodthirstiness was higher than it had ever been. But, feral Logan wasn’t meant to last -- once he got his adamantium bones back, the old slightly-less-feral Wolverine returned.

16 BLOB: STRETCHING

Blob Secondary Mutation

During the recent “Cry Havok” arc in X-Men Blue, numerous characters developed secondary mutations thanks to Havok’s secret weapon: Mothervine. The mysterious virus caused humans to develop mutations and mutants to develop new mutations. Unlike most comic book arcs, the results of the short-lived Mothervine invasion weren’t erased overnight. The characters who were changed were changed for good, including The Blob.

Blob somehow fell into Miss Sinister’s clutches and became a Mothervine guinea pig. His secondary mutation allowed him to stretch his body to a great extent, but with a serious price. The mutation is hard to control and when he first manifested it, he stretched himself too far and painfully melted into a puddle.

15 GAMBIT: FUTURE INSTINCT

Gambit Secondary Mutation

Gambit is a kinetic energy wonder, with the mutant ability to “charge” objects before throwing them with incredible speed. His sight is vital when fighting since he needs to be able to see his target in order to hit it. After a traumatic event leaves him blind, a secondary mutation kicks in that allows Gambit to stay an X-Men field member: clairvoyance.

Gambit’s ability did not give him the power to consciously look into the future. Instead, his secondary mutation acted like a warning system. He could sense danger and react to it. Gambit got his sight back not long after losing it, so we aren’t sure how powerful Gambit’s ability truly was.

14 MASQUE: ALTER OWN APPEARANCE

Masque Secondary Mutation

One of the creepiest (if not the creepiest) characters in the X-Men universe is Masque. If you aren’t familiar with this guy, you’re lucky. He’s a mutant Morlock armed with the ability to change a person’s appearance in any way, shape, or fashion. In the ‘80s he gave Jean Grey tentacle arms and erased Kitty Pryde’s face. The last thing this guy needed was a secondary mutation to make him even more powerful.

Of course, that’s exactly what happened. For most of his life, Masque couldn’t alter his own unfortunate appearance. At some point, that changed, allowing Masque to take many different forms and reel in more unsuspecting victims.

13 BEAST: FELINE FEATURES

Beast Secondary Mutation

Beast’s mutant ability was originally his brain -- the blue fur came later. In his first appearance, Beast looks like a typical teenager with just a hint of something animalistic lingering beneath. Due to numerous bouts of self-experimentation, plus a few freak accidents, Hank went through a secondary mutation that produced the Beast we know today.

Over the years, his secondary mutation has grown and developed considerably. In some series’, he looks more apish and in others, like Grant Morrison's New X-Men, more feline. The blue fur also comes with some sharp teeth and claws as well as a serious strength upgrade. As much as Hank something loathes his blue coat, his secondary mutation regularly comes in handy during fights.

12 TOAD: FLAMING TONGUE

Toad Secondary Mutation

Having frog-like qualities might not initially sound very promising, but Mortimer Toynbee has really made the best of it. His prehensile tongue, superhuman reflexes, and acidic saliva quickly made him a key player on Magneto’s infamous Brotherhood of Evil Mutants. In recent X-Men comics, Toad’s powerset has seen a big upgrade with the addition of a secondary mutation: a flaming tongue.

All of Toad’s other characteristics mimic a toad, so we’re a little unsure why he developed this strange ability. Still, we have to admit that it’s kind of awesome. Beyond how gross and unrealistic it is, it’s a surprisingly handy mutation. What’s worse than getting hit with a giant prehensile tongue? Getting hit with one that’s on fire.

11 JEAN GREY: REIGNITE POWERS

Jean Grey Secondary Mutation

Yes, we’re talking about Jean Grey, but no, we aren’t talking about the Phoenix. Technically, none of Jean’s Phoenix powers are secondary mutations, so we’re not adding her to the list for the fiery bird. We’re adding her to the list because she lost then “magically” regained her powers like it was no big deal.

After Jean absorbed Psylocke’s telepathy, she lost her telekinesis... for a little while. Without much explanation, Jean’s telekinesis slowly reemerged. Beast connected it to a secondary mutation, since there wasn’t another viable answer. With this unique mutation, Jean never has to worry about someone taking or her losing her powers ever again. She might even be capable of awakening mutant potential in people, but that’s still TBD.

10 WOLFSBANE: WOLFPACK

Wolfsbane Secondary Mutation

Rahne Sinclair , aka Wolfsbane, underwent a secondary mutation during "Secret Empire". Like many other X-Men at the time, Rahne became an agent for Emma Frost’s mutant-oasis nation. Rahne’s secondary mutation manifested under some mysterious circumstances that probably have to do with Emma being just the worst. Still, she came out on the other side, more or less... intact.

Wolfsbane has always been capable of transforming into a wolf, but after her secondary mutation, she could somehow transform into a pack of wolves (think of Multiple Man, but furrier). Her general lupine characteristics (claws, teeth, etc.) also became stronger and sharper. Secondary mutations don’t always make a mutant a better fighter, but in the case of Wolfsbane it multiplied her combat potential exponentially.

9 ARCHANGEL: HEALING FACTOR

Angel Secondary Mutation

Angel (or Archangel) is a confusing character -- well, maybe complex would be the better word. We love Angel as much as the next person, but it’s really hard to keep up with everything that’s happened to the poor guy. Originally, his only power was flight, but over the years, Marvel writers have added tons of stuff to his resume, including being both Apocalypse's Death and Life seed and having life-saving blood.

That’s right: Angel has healing blood. Since nothing is for certain in Angel’s life, there are a few possibilities as to why Angel’s blood can heal. For this list, you only really need to know one: secondary mutation.

8 UNUSCIONE: MOTHERVINE UPGRADE

Unuscione Secondary Mutation

Similar to Blob, the less than popular mutant Unuscione got a huge power boost after Havok unleashed Mothervine on the world. As one of the lesser known characters on the list, a lot of X-Men Blue fans might not have even noticed her short appearance. She appears to be fighting against the X-Men, but closer inspection reveals that her ability to create bio-electric blasts has gone beyond her control.

This version of Unuscione is incredibly powerful, but that isn’t necessarily a good thing for her. Unuscione’s powers derive from a psionic exoskeleton that she can make around herself. After Mothervine, Unuscione’s powers became so great that her exoskeleton began to hurt both her and her allies.

7 SIRYN: SONIC CONTROL

Siryn Secondary Mutation

Siryn is another character that may or may not have undergone a secondary mutation. Writers don’t always make it clear, which means readers are forced to infer. In the case of Siryn, we’re pretty sure she manifested some latent genetic potential in the pages of X-Factor, where she’s seen staying true to her mythological namesake.

Siryn, like her father Banshee, has a mutant sonic scream. After years of showing off her ear-drum-destructive voice, Siryn began showing a different power: sonic trance. Like a real Siryn, Theresa can use her voice to send others into a hypnotic state. She can also use her voice to subconsciously control someone. It isn’t always impressively strong, but Siryn can (usually) get someone to do what she wants.

6 EMMA FROST: DIAMOND SKIN

Emma Frost Secondary Mutation

The most famous secondary mutation on the list has to be Emma Frost’s signature diamond skin. Grant Morrison first introduced Emma’s shiny new mutant ability in the 2001 series, New X-Men. Emma’s secondary mutation developed after the bombing of Genosha, which took out practically everyone on the island except for her. The only thing that saved her was her diamond coating.

Since then, Emma’s secondary mutation has become just as iconic as her telepathic powers. Because secondary mutations aren’t usually a character’s main ability, writers frequently ignore or forget about them. Thankfully, that’s not the case with Emma. Her nearly indestructible diamond skin, which she can change into at will, is a common plot point in X-Men comics.

5 BLACK TOM: HALF-PLANT

Black Tom Secondary Mutation

Black Tom’s secondary mutation is the perfect example of too much of a good thing. His mutant power gives him the ability to create huge blasts, using wood as a power conductor. After Cable seriously injured him, doctors grafted pieces of wood over Tom’s wounds, thus allowing him to use his powers more efficiently. The surgery worked, but it later spurned a secondary mutation that turned Tom into a half-man half-plant hybrid.

Armed with this second mutation, Tom could grow to any size, heal any wound, and control any plant. He could also absorb any organic being’s life force, which ultimately got him in a lot of trouble. By the end, before he lost his mutation in M-Day, Tom was more plant than man.

4 POLARIS: HULKED OUT

Polaris Secondary Mutation

Most secondary mutations require a traumatic experience to kickstart their manifestation. For Emma, it was the bombing of Genosha, for Elixir it was healing himself from the brink of demise, and for Polaris it was losing her famous magnetic powers.

Before most X-Men readers had even heard of the term secondary mutation, villainess Zaladane stripped Lorna of her mutant ability, leaving her completely vulnerable... for about half a second. The jolt of losing her powers forces Polaris’ latent secondary mutation to evolve. She grew in height and gained super strength and durability. After regaining her magnetic powers, Lorna lost her Hulk-like traits. But, honestly, we would’ve loved to see a little more of the Hulked-out Polaris.

3 HAVOK: BODY-HOPPING

Havok Secondary Mutation

During the Mutant X series, a cosmic force pulled the alternate reality versions of Alex Summers together. At the moment, Havok didn’t know he was undergoing a secondary mutation since it didn’t involve a traumatic moment or an artificial boost. We don't immediately see the effects of this “mutation” (if it is a mutation or something even more confusing). It isn’t until Alex passes away on Earth-616 and wakes up in a new body that the change becomes evident.

Havok has the ability to move his consciousness to other versions of himself. So, in an essence, he can’t truly “perish”. With more practice, Havok could use this connection he has to other versions of himself to do other things, like participate in fights and telepathically communicate.

2 QUENTIN QUIRE: INCORPOREAL STATE

Quentin Quire Secondary Mutation

Quentin Quire is overdramatic (it’s a vital part of his character) and his secondary mutation is no different. It took overdosing on the X-gene enhancer drug known as “Kick” to spur Quentin’s secondary mutation. The overdose caused his telepathic powers to become so powerful that his own psionic energy was burning his body alive. To compensate, his secondary mutation transformed his brain into faster-than-light energy and sent Quentin into a different plane of existence.

Quentin’s secondary mutation didn’t end him. Rather, it made him into a non-corporeal life-form that had contact with every living mind on the planet. Quentin never discovered how to use his secondary mutation fully, but if he ever did, the possibilities would be endless.

1 KITTY PRYDE: TIME TRAVEL

Kitty Pryde Secondary Mutation

We haven’t mentioned the X-Men film franchise yet, partly because it doesn’t talk about secondary mutations very often. The only time it really comes up is in X-Men: Days of Future Past, where Kitty develops the ability to time travel. Her secondary mutation allows her to send an individual’s consciousness to a different timeline. While there, the individual can manipulate past events and cause changes to the timeline.

The film’s writers only added Kitty’s strange secondary mutation so that they could send Wolverine back in time. It never occurs in the comics and hasn’t occurred in the movies since Days of Future Past. Still, it’s an incredible power that can drastically change the world and everyone in it, which is why it’s number one on our list.