Shadow King (Legion)

Amahl Faurok, also known as The Devil with the Yellow Eyes and the Shadow King, appears as the primary antagonist of Season 1 of the FX-original Marvel Television series Legion. He is a demonic parasite, seeking to take control of David Haller's body and use his reality-bending abilities for sinister purposes. He is an adaptation of the X-Men villain known as the Shadow King.

He is portrayed by actor Quinton Boisclair in his standard form, and by Aubrey Plaza while taking the form of Lenny Busker.

Origin
The Devil with the Yellow Eyes is a centuries-old parasite-like creature that seemed to originate from the Astral Plane, a dimension of reality that can be accessed by a powerful telepathic mutant. Through unknown means, he came to confront Professor Charles Xavier, the leader of the X-Men and a powerful telepath. He was able to defeat the Devil, but was unable to destroy him.

Seeking revenge and desiring to come to the real-world and become more powerful, he tried to locate Xavier's son David Haller, who was capable of controlling reality. Xavier had him sent away for his protection, later adopted by the Haller family, but the Devil held onto him and manifested himself in several forms, including his "dog" King and his friend Benny. However, he was only ever visible to David, as his sister Amy Haller says that they never had a dog named King.

Eventually, David, unaware of his powers and considered very dangerous, is diagnosed with schizophrenia and sent to Clockworks Psychiatric Hospital for treatment.

Chapter 1
The Devil is first hinted at in a vision that David has, which depicts himself eating what appears to be black tape, as a voice says "The Devil with the Yellow Eyes".

The Devil first gets his chance to latch onto David's powers when he and fellow mutant Sydney "Syd" Barrett accidentally switch bodies. While David ends up in Syd's body (as physical contact with her causes her to switch bodies with whoever she touches) and is confused, Syd ends up in David's body. The Devil, seeing the opportunity, manages to get Syd to expel David's powers, causing people in the building, including David's friend Lenny Busker, to be pulled through the walls of the building. Lenny, meanwhile, ends up getting stuck in the wall, killing her and causing blood to cover the wall. Later when Syd and David's minds are somehow put back where they belong, David is freed by a band of mutants after being captured by Division 3 and brought to a mutant safe haven known as Summerland, run by mutant Melanie Bird.

Chapter 2
David, seeking to better understand his powers, is put into a room with Melanie and Ptonomy Wallace, where Ptonomy takes them through David's memories, seeking to find proof that he has mutant powers. While sorting through the memories, David meets Lenny Busker, who appears to be present in his memories through unknown means (she is really a manifestation of the Devil). In his memories, they find that David had previously taken drugs with "Lenny" in order to drown out the voices he hears due to his telepathy. While the three observe the memory, David's present self hears the Devil's sinister laugh. He then steps in through the kitchen door, glaring at David with an evil grin, while Ptonomy and Melanie are unable to see him.

Later, David is put into an MRI scanner in order to determine how his powers work. As he lies there in silence, he sees a vision of Amy at Clockworks, but she's in danger. He then looks up to see the Devil there, who looks down on him and grabs his legs, trying to pull him out of the machine; David then screams in fear and anger, causing the Devil to disappear and the MRI to be teleported outside Summerland.

Chapter 3
To be continued

Chapter 4
To be continued

Chapter 5
To be continued

Chapter 6
To be continued

Chapter 7
To be continued

Chapter 8
To be continued

Trivia

 * The Devil has been likened to Killer BOB from Twin Peaks by series creator Noah Hawley, due to them both being demonic creatures with little information existing about them in the initial part of their respective series.
 * The Devil also behaves similarly to the Man in Black from Lost during Seasons 1-4, both being shrouded in mystery and appearing very few times to the protagonists, or even to the audience. They are both also evil demonic beings who seek to damage the fabric of reality.