In recent months, Sabretooth has returned to his old ways as a villainous mercenary. Avengers & X-Men: AXIS inverted the virtually immortal mutant into a hero, and whereas most characters inverted at the beginning of the event were returned to their normal alignment by the story's end, Sabretooth avoided this fate for over three years. In his time as a hero, he set out to right his wrongs, working alongside many of his old enemies to take on the evils in the Marvel Universe. Finally, Sabretooth has been reinverted -- and just in time to attack his resurrected archnemesis, Wolverine. With the stage set for Sabretooth to unleash hell on the MU, we've decided to take a look at 20 lesser-known facts about one of Marvel's most savage mutants.

At first look, there doesn't appear to be much to Sabretooth -- he may just come across as little more than a villainous version of Wolverine. But on closer look, Sabretooth turns out to be a complex character with a history of surprising facts, some which even stir up sympathy. For one thing, Sabretooth has a pretty good reason to hate the X-Men. He's been imprisoned by them, made their pet, and forced to fight for them on several occasions. Of course, this isn't to say that Sabretooth is a saint. For all of the terrible things done to him, he's done plenty of terrible things to others, notably Wolverine and fans will know the two of them to be mortal enemies, but do they know why? Do they know just how much red they've got in their ledger during their century-long feud?

20 MEMBER OF THE 1959 AVENGERS

When fans think of the original Avengers, they probably think of Iron Man, Thor, and the rest of Avengers who debuted in Avengers (Vol. 1) #1. However, in New Avengers (Vol. 2) #12, Nick Fury revealed that he assembled a much different Avengers team in 1959.

The '59 Avengers was a black ops squad, consisting of Kraven the Hunter, Silver Sable, Namora, and Sabretooth, among others, aimed at preventing the Red Skull form organizing remaining evil forces into a new organization. Despite Sabretooth's violent tendencies costing the team on several occasions, Creed proved to be an invaluable asset for Fury.

19 INITIALLY AN IRON FIST VILLAIN

Fans may be surprised to learn that Sabretooth had been hanging out in Marvel comics for nearly a decade before he caught up with Wolverine. In fact, he didn't feature in an X-Men comic until 1986 in X-Factor (Vol. 1) #10. Sabretooth was introduced in '77's Iron Fist (Vol. 1) #14, and remained as an Iron Fist antagonist primarily for the following years.

In his debut, Sabretooth's job as a mercenary brings him into conflict with Iron Fist. As such, his hunting ability is emphasized, but when he goes toe-to-toe with Sabretooth, he stands no chance. In later appearances, Sabretooth would grow increasingly more dangerous in hand-to-hand combat.

18  EARLIEST ENCOUNTER...?

Sabretooth's earliest known encounter with Wolverine came at some time during the beginning of the 20th century. The meeting is recalled via flashback in Wolverine (Vol. 2) #10. Triggered by a bar fight unfolding before him, Logan remembers when Sabretooth arrived at a bar that he and Logan used to frequent, admitting to having slain Wolverine's beloved, Silver Fox.

Sabretooth's confession leads to an all-out brawl between the two mutants. Before long, it's hardly a contest -- Sabretooth is completely overwhelming Logan, leading the latter to attempt to escape the fight. After beating Logan into submission, Sabretooth spares his life. However, the truth of this encounter would prove to more complicated, as a later event would reveal.

17 CAREER BACKSTABBER

Sabretooth isn't somebody we'd want on our team. Among Sabretooth's character defects is his proven tendency to turn on his teammates and friends. Following his time with the '59 Avengers, Sabretooth joined a black ops group called Team X. Here he fought alongside Wolverine and Maverick, but it didn't take long for him to sell out his teammates.

And when he's not betraying his fellow operatives via shady dealings, he's turning on his teammates out of uncontrollable bloodlust as was the case in later years when he participated on various X-Men squads. Considering his track record, it's a miracle he didn't turn on Nick Fury and the '59 Avengers.

16 RELATIONSHIP WITH HOLO

In the century that they've known each other, Sabretooth and Wolverine have compiled plenty of reasons to hate one another. One of Sabretooth's strongest motives for hunting down Wolverine is that Sabretooth blames him for the demise of Holo. Holo, a mutant who could create holograms, met Sabretooth when they joined Wolverine on a mission to stamp out anti-mutant forces at work in the government.

Sabretooth fell in love with Holo and began to lose interest in his characteristic ultraviolence. However, right when he thought he could settle down for a quieter life, tragedy struck. Holo passed away during a final conflict, prompting Sabretooth to blame Wolverine for leading them into trouble.

15 SABRETOOTH AND CONSTRICTOR

Before Sabretooth became integral to Marvel's X-Men stories, he often teamed up with Constrictor to take on Iron Fist and Luke Cage. Following Sabretooth's initial embarrassing defeat at the hands of Iron Fist, he partnered up with Constrictor, a supervillain who's gone up against nearly all of Marvel's heroes.

Together with Constrictor, Sabretooth didn't fare much better. Iron Fist and crew repeatedly overcame the duo, and it seemed as if Sabretooth would remain a second-rate villain forever. It didn't take long for Sabretooth to become fed up with his partner and nearly take his life. Once the partnership concluded, Sabretooth emerged into the X-Men's world as a formidable foe.

14 IT WAS PSI-BORG'S FAULT

Psi-Borg, a cyborg possessing psychic abilities, was a partner of the Weapon X Program, leading to his first meeting with the members of Team X. Psi-Borg was responsible for capturing Sabretooth and Wolverine, leading to Weapon X's experimentation on the two. The event tampered with Sabretooth and Wolverine's memories, and they wouldn't discover the truth of their past until years later.

When they finally returned to Weapon X to discover the truth, Psi-Borg possessed Sabretooth's mind and sent him into a rage. In this state, Sabretooth slew Silver Fox, revealing Logan's memory of her first passing had been implanted by Psi-Borg.

13 TAMED AND CIVILIZED

Sabretooth's life dramatically changed when he met a telepath named Birdy. Birdy helped Sabretooth by using her powers to relieve him of his bloodlust. Finally calmed down, Sabretooth traded in his savagery for more of a business-savvy approach to crime -- the new Sabretooth wore power suits and made deals with organizations like the Hand.

It looked as if his insatiable thirst for chaos was finally behind him. But, as with Wolverine, tragedy follows Sabretooth wherever he goes. In Sabretooth (Vol. 1) #4, Birdy was stabbed by Sabretooth's long-lost son, Graydon. The tragedy left Sabretooth more lost and savage than ever before.

12 FORCED INTO X-FACTOR

After spending time as a prisoner of the X-Men, Xavier's team decided that they could use Sabretooth. The mutants placed a collar around Sabretooth's neck that would harm him whenever he attempted to attack them, and then threw him on the latest iteration of X-Factor. In X-Factor (Vol. 1) #123, Sabretooth officially joined Forge, Wild Child, Polaris, and Shard against a new villain known as Hound.

Of course, it was only a matter of time for Sabretooth to rebel against the team. Sabretooth allies himself with Zero Tolerance who helps to break him free of the collar, at which point Sabretooth is unleashed onto X-Factor.

11 GAMBIT SAVED HIS LIFE

Considering their history, Sabretooth would've expected Gambit to be among the last people to save his life. Sabretooth and Gambit first met when they were recruited by the Marauders. After realizing that the Marauders would go too far, Gambit tried to leave the group, resulting in Sabretooth attacking him.

Despite Sabretooth's best intentions, Gambit survived the attack and was able to alert the X-Men to the Marauders' plot. Years later, Apocalypse ripped the adamantium out of Sabretooth, leaving him on the brink of his end. Gambit discovered the struggling mutant and saved his life in exchange for Sabretooth leading Gambit to one of Mr. Sinister's bases.

10 SABRETOOTH NOIR

Writer Stuart Moore offered us a very different take on Sabretooth in the pages of Wolverine Noir. The story featured a version of Wolverine where he's a private detective working in New York during the '30s. Sabretooth, known in the story simply as Victor Creed, is a shady owner of a hotel and boxing club, involved in organized crime.

Logan's detective work brings him to Victor's boxing arena where they slug it out, resulting in Logan quickly falling before the much larger Victor. Later in the story, Victor and his thugs capture Logan, culminating in a firefight, which Victor just nearly escapes with his life.

9 COERCED INTO THE X-MEN

Sabretooth has bad history with the X-Men. Aside from aligning against the team of mutants, the X-Men have also forced him to take part on two of their teams. The second instance of this coercion came after Sabretooth discovered a race of superhumans known as the Children who were planning to conquer humankind.

The Children frightened Sabretooth enough for him to seek help from the X-Men. In return for protection, Sabretooth joined the X-Men in their fight against the Children -- well, not exactly out of his own free will. He was implanted with nano-sentinels and forced to be an X-Man even after the Children had been defeated.

8 THE MURAMASA BLADE

Sabretooth and Wolverine have one very specific weakness in common: the Muramasa Blade. The blade was forged by the master swordsman Muramasa, and imbued with a piece of his own soul, thus bestowing upon it various mystical properties. Among the sword's magical abilities is the ability to disable an opponent's healing factor -- which is why it can end virtually immortal mutants such as Sabretooth and Wolverine.

Wolverine used the Muramasa Blade to do just that to his long-time nemesis Sabretooth in Wolverine (Vol. 3) #54. However, fans would soon learn that there was more to meet the eye, and that the true Sabretooth was alive and well.

7 CLONES

The end of Wolverine (Vol. 3) #54 seemed to put a certain end to Sabretooth, what with his last encounter with Logan and the Muramasa Blade. However, it turned out that the Sabretooth that Wolverine eliminated was just a clone. Romulus, the puppet master behind many of the events in Wolverine's life, had deceived Wolverine into thinking he'd finally taken out Sabretooth.

The mastermind had actually created several clones of Sabretooth, dispatching them at his leisure. Logan discovered the ruse in Wolverine (Vol. 2) #310 and made quick work of the clones. The real Sabretooth had been in hiding, biding his time until he'd return to terrorize Wolverine once more.

6 MYSTIQUE AND CHILDREN

Early on in their careers as mercenaries, Mystique and Sabretooth had an affair. Unbeknownst to Sabretooth, Mystique gave birth to Graydon Creed and gave the baby up to adoption. Years later, Graydon would discover the truth of his parentage and seeing as how it had been mutants that'd abandoned him, Graydon found a reason to hate mutantkind, motivating his radical political agenda to eliminate them.

As for the Age of Apocalypse version of Sabretooth, it was suggested that Nightcrawler was his and Mystique's offspring. In that reality, Sabretooth also adopted the young mutant Blink after he rescued her from Apocalypse's slave pens.

5 FATHERS, SONS, AND BROTHERS

Depending on the reality, Sabretooth and Wolverine's relationship differs dramatically. While in the main 616 Universe they seem to just be drawn to one another due to their similar personalities and powers, they're often related in alternative realities. In Chris Claremont's X-Men Forever reality --  an offshoot of his in-cannon run on X-Men comics from 1975-91 -- Sabretooth is revealed to be Wolverine's father.

After Wolverine falls in battle, Sabretooth honors his son by joining the X-Men. In the Ultimate MU, Sabretooth insists that he's Wolverine's son, although Logan doubts these claims. Lastly, in X-Men Origins: Wolverine, the two are portrayed as half-brothers, sharing the same father.

4 LOGAN'S LEGACY

There were long-term consequence for Sabretooth stemming from Avengers & X-Men: AXIS. The series saw heroes inverted into villains and vice versa as a result of a spell cast by Doctor Doom and Scarlet Witch. By series' end, most of the characters had been returned back to normal -- save for Sabretooth due to being shielded from the reinversion spell.

Now, apparently a permanent hero, Sabretooth joined the Unity Avengers and then Magneto's X-Men, taking on villains like the High Evolutionary. After Wolverine's passing, Sabretooth doubled-down on his allegiance to the side of good, vowing to be live up to Logan's legacy.

3 MEDIUM AWARENESS

Few characters tap into moments of medium awareness -- the ability to break the fourth wall by suggesting that they recognize their status as comic book characters. This ability is mostly associated with Deadpool, but on at least one occasion, Sabretooth has displayed medium awareness.

Unsurpisingly, the moment happened when Sabretooth went up against the Merc with a Mouth. In Deadpool (Vol. 3) #34, which features several running gags, including artist Rob Liefield's aversion to drawing feet, Sabretooth says that he knows that Deadpool is based on DC's Deathstroke. So, not only do we get a moment of medium awareness from Sabretooth, but also the rare reference to Marvel's competing company.

2 EXILE

Of all of the alternate versions of Sabretooth, his Age of Apocalypse counterpart has the most extensive history. The character originated in the "Age of Apocalypse" crossover, but really blossomed in the series Exiles. In the AoA reality, Sabretooth was an X-Man, adopted a young mutant named Blink, and spent years raising mutant children.

He later joined the Exiles, a group of mutants pulled from various universes, focused on protecting the multiverse. Sabretooth even rose to lead the team at one point, organizing attacks on numerous multiversal threats. Unfortunately, Sabretooth would eventually fall in battle, as in Astonishing X-Men (Vol. 1) #60, Sabretooth and several of his comrades were eliminated by ultra-powerful entities.

1 HERALD OF GALACTUS

The Age of Apocalypse version of Sabretooth has gone through a number of rare experiences that his 616 counterpart hasn't even come close to. One such experience was when he became the herald of Galactus for a brief period. In Exiles (Vol. 2) #88, the team goes up against a rogue Silver Surfer. In order to acquire to the ability to defeat Silver Surfer, Sabretooth submits to Galactus.

As Galactus' herald, Sabretooth receives the Power Cosmic -- a cosmic energy that allows for various abilities, including energy projection and transmutation of matter. The newly empowered Sabretooth quickly dispatches of Silver Surfer before returning the Power Cosmic to Galactus.