OREANDA-NEWS  Tonight's Legion episode (read our review of Legion: "Chapter 7" here) answered a number of running questions about the mysterious "Devil with Yellow Eyes" and its true connection to David Haller. We now know that this character is actually the Shadow King, a long-standing X-Men villain whose rivalry with Charles Xavier dates back decades. And though Xavier wasn't specifically referenced by name in this episode, it seems that rivalry has translated over into the show.

For those not familiar with the Xavier/Shadow King dynamic in the comics, we figured now would be the perfect time to break down their shared history and how Legion's handling of the Shadow King compares to the source material.

While the TV series portrays the Shadow King as an especially powerful mutant parasite, in the comics it's more of a psychic monster created by the collective dark side of human consciousness. The Shadow King is a being without a body. It lives solely on the astral plane, a realm where it possesses almost limitless telepathic power and only someone as powerful as Charles Xavier stands a chance of opposing it.

However, as in the show, the Shadow King of the comics has been known to possess the bodies of human hosts. Its most commonly known host is an obese Egyptian psychic named Amahl Farouk. These hosts allow the Shadow King to more directly influence human affairs, or simply enjoy the hedonistic pleasures of the flesh. However, the creature is also much more vulnerable when it takes physical form.

The original encounter between Xavier and the Shadow King played out a bit differently in the comics than how it does in Legion. In the show, we learn that Xavier was motivated by a desire to protect his infant son from the Shadow King's parasitic clutches, hence why he placed young David into hiding. But in the comics, David didn't factor into their original battles. As a matter of fact, Xavier wasn't even aware of David's existence for a long while.

In the comics, this rivalry first began when a young Xavier traveled to Egypt and detected Farouk's powerful psychic presence. Farouk tried to compel Xavier to join him and pool their abilities together to become world-class criminals. Xavier refused, naturally, and defeated his new foe in a game of Astral Plane Mortal Kombat.

The Shadow King has the distinction of being the very first evil mutant Xavier encountered in his travels, and thus is one of the primary inspirations for the creation of the X-Men in the first place. Even then, Xavier knew that Farouk was just the first of many mutant threats the world would be facing in the years to come.

That battle in Eqypt was the first of many encounters between Xavier and the Shadow King. However, when the villain next resurfaced, he didn't target David as he does in Legion, but another young mutant named Karma. A powerful psychic in her own right, Karma has the ability to project her consciousness and take control of other peoples' bodies. Interestingly, that's very similar to the power displayed by David's girlfriend, Syd, in the show. Coincidence, or something more?

In any case, Karma was one of the founding members of Xavier's New Mutants, a team of teenage mutants training to become the next generation of X-Men. She was possessed by the Shadow King in an early mission and believed by her teammates to have died. The Shadow King used his new host body to rebuild its criminal empire. Reflecting its dark, hedonistic personality, Karma devolved into an obese shell of herself while possessed by this psychic demon. Luckily, she was eventually freed by her teammates and managed to defeat the Shadow King on the astral plane just as Xavier did before her.

The Shadow King's connection to David Haller didn't come into play until a 1991 crossover storyline called "The Muir Island Saga." In fact, Xavier himself didn't discover David's existence until after he had formed the New Mutants. During this period, the psychologically fragile David was being kept as a patient on Muir Island. Unfortunately, the entire island was overtaken by the Shadow King, who invaded David's body and used him to fuel a new psychic attack on mankind. The Shadow King's plan was to increase humanity's feelings of hatred and fear, allowing it to feast on the negative energy and become exponentially more powerful.

Fortunately, Xavier was able to confront the Shadow King on the astral plane and, powered by the psychic support of his students, defeat his old enemy once again. The bad news is that the fight left Xavier paralyzed all over again and David's mind shattered.

Like most comic book supervillains, the Shadow King never truly dies, and it's returned several times in the years since to do battle with the X-Men. But with Xavier having spent much of the last decade's worth of X-Men stories either retired or dead, the Shadow King has mostly shifted the focus of its wrath to other telepathic mutants like Psylocke.

Where the Shadow King's story will lead on Legion remains to be seen, but the character clearly has plenty of X-Men stories to be mined if showrunner Noah Hawley and his team decide to keep the character around in Season 2 next year... and beyond.

Jesse is a mild-mannered writer for IGN. Allow him to lend a machete to your intellectual thicket by following @jschedeen on Twitter, or Kicksplode on MyIGN.