"It wears a human face. Be careful. He wears a human face."

-- Brubaker

When "Legion" offered the first unnerving glimpses of the Devil With Yellow Eyes, a grotesque entity that looms in the corners of David Haller's fractured memories, Marvel Comics fans immediately began to search for its connection to X-Men mythology. The alien Mojo was offered up as a potential candidate, if only because of the physical similarities, but so too was the Shadow King, a similarly yellow-eyed mutant who has menaced the X-Men for decades. It was easy to disregard Mojo, as his powers and M.O. don't match, but the Shadow King remained an outside possibility. Yet he didn't seem likely, as series creator Noah Hawley had chosen to pluck David Haller out of the comic books but ignore most of the other elements of Marvel's mutant universe. (Well, except for the word "mutant.")

However, with this week's episode of "Legion," we may have to give the Devil, and the Shadow King, his due. Or at least a Shadow King-like character.

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David Haller returned from the astral plane, and from his conversation with the long-missing Oliver Bird, a changed person. He's no longer the fragile little boy who questioned his powers, and his sanity. He's confident, even cocky, and in tune with his vast psychic abilities, so much so that he can whisk Syd away to a beach-side white room within his mind. There they can touch, kiss, have sex; it's everything they've wanted. Except, of course, it's not. As with the rest of David's world, whether the physical or the imagined -- "Real, fake, it's all the same" -- something powerful, something evil, lurks just at the edges. In the white room, it manifests in the bugs that crawl on the bowl of strawberries, marring an otherwise-placid setting, and in the red light that filters through the curtains and seeps in beneath the bathroom door.

Yes, David Haller has changed, but not for the better. He moves differently, he talks differently; the confidence he now exudes is almost that of a predator. When he informs Melanie that he met her husband, who's been lost to her for more than two decades, it's not out of kindness or concern. He seems to be probing, searching for a weakness, and he finds it. "Did he ask about me?" asks a teary-eyed Melanie. "He remembers very little, I think," David responds coolly. "Facts. He makes his own reality now. But there was a moment ..." But what in other circumstances might be interpreted as an attempt to salve hurt feelings here seems mean-spirited, as if David is merely toying with her, the way a cat would treat a mouse.

Although Melanie is clearly distracted by news of Oliver, and by hope that he might be returned to her, she's not blind to David's transformation. When David informs her he's going to rescue his sister Amy, Melanie warns that Division 3 will be ready and waiting for him, and that such an assault takes planning. When that doesn't work, she uses Oliver as a cautionary tale: He was very much like David, once upon a time, and created his own world. And then one day, he simply never returned. She even expresses her concerns to Syd, who acknowledges the changes to David but doesn't recognize any warning signs; she's just elated to be able to be with him, even if it's only within a room created by his mind. Heck, she didn't even tell him what they discovered about his ex-girlfriend and former therapist.

In fact, Syd is so unfazed that she gleefully agrees to set off with David to free his sister, leaving the Summerland crew behind. "It'll be fun. Kick some ass, save the girl, get a snack," David says, sounding more like Lenny than himself. But first, there's sex in the white room, which is bathed in a blue light that will undoubtedly evoke the "vapor" David and Lenny (or is that Benny?) got high on in his old apartment. However, nothing can keep the red at bay for long. With Syd asleep, David is coaxed, or perhaps coerced, by Lenny to forget these "losers" and attack Division 3 by himself. It'll be fun, after all.

Awaking to find David gone, Syd informs Melanie, who's busy plotting an assault on Division 3. Rallying the troops, Melanie orders the attack to move forward without a plan -- not, as Ptonomy suggests, because she thinks David can bring Oliver back, but because he's too powerful to risk losing him to their rivals. They needn't have worried, because when the Summerland team (Melanie, Ptonomy, Syd and the unnamed telekinetic guy) arrive at Division 3's bunker, they find almost-unimaginable carnage. Amid the fire and debris are the bodies, and body parts, of D3 soldiers, some of whom are stuck half in and half out of concrete, like Lenny at Clockworks. The scene isn't much better inside, where arms and legs are strewn throughout halls and stairways. However, there are still signs of life: Still in his cell, even after David rescued Amy, an agitated Dr. Kissinger repeatedly asks Syd to free him, only to be left behind once more.

We're given an unsettling glimpse of the grisly events that unfolded here as Melanie & Co. access the building's security footage, which depicts an almost-joyful David using his powers to kill one soldier after another. If that's not confirmation enough this isn't David -- or at least it's not only David -- an infrared camera captures the unmistakable form of the Devil With Yellow Eyes in his place. With his dying breaths, D3 administrator Brubaker tells Syd and Ptonomy, "We were wrong. We had it all wrong. He took her, the sister. He knew he'd come; we were ready. We thought we were ready. So much power. It wears a human face. Be careful. He wears a human face."

Meanwhile, Cary Loudermilk arrives at a similar conclusion miles away at Summerland. Dividing his time between healing and arguing with a wounded Kerry and reviewing David's MRI, Cary glimpses in footage both the Devil With Yellow Eyes and an 8-year-old David. It's apparently a eureka moment, as Cary immediately contacts Melanie, and inadvertently echoes Brubaker's conclusions: "This monster isn't David, it's a parasite of some kind -- another consciousness of some kind inside of him. This thing burrowed into David's brain when he was a boy, maybe even a baby, and it has been there, feeding on him, ever since."

He determines it's an enormously powerful older mutant whose consciousness separated from its body. It's lived within David for 30 years, rewriting his memories to hide itself from prying eyes, and minds. It transformed David's drug friend Benny into Lenny, scrubbed important events -- What did the stars say? -- and even created a childhood pet when there was none. (More on that last part in a moment.) It's in those descriptions that the Devil With Yellow Eyes is most like the Shadow King. He's a psychic parasite capable of possessing a host and manipulating the astral plane. The Marvel Comics version is said of have been born "when the first dreams came in night, in the first nightmare," and feeds on hatred and violence. That certainly sounds like the Devil With Yellow Eyes, whom we must assume took firmer control of his host during David's visit to the astral plane.

Now add to that David's beloved dog, which we now know never actually existed. It was a manifestation of this Devil, just like Lenny and the Angriest Boy in the World. And its name of this imagined pet that David would talk to as a child? King. That can't be a coincidence. King appears again in the red-hued bathroom of the white room, as a frightened David plucks "The Rainbow Connection" on a banjo while singing with a shaky voice, and again in a re-creation of his childhood home, where he and Lenny question, and menace, a "rescued" Amy.

What should be a comforting familiar setting is transformed into a haunted house for Amy as David and a sharp-dressed Lenny root for information. "I want to know your secret," David says. "I can smell it, see, this secret. Probably always, but now it's really clear: You know something about me." That something turns out to be that he's adopted, a revelation that undoubtedly fuels hopes for a cameo by Charles Xavier.

Trailed by The Eye, Melanie, Syd & Co. arrive at what they realize may not be David's real childhood home, only for their suspicions to be confirmed when they can't make any sounds. Communicating by hand signals and lip-reading, they're soon joined Cary, who has created a device that he believes may temporarily separate the Devil from David, and then by Kerry, who brought along a spiked bat.

Despite brushes with the Angriest Boy and then Lenny -- "This is not the talking place, this is the listening place" -- they finally reach David, only for The Eye, in the guise of the telekinetic guy, to barge in with machine gun blazing. A quick-thinking Syd shouts, "David, white room! Now!," and the two of them are whisked away into his mindspace. But they're far from safe, as the Devil With Yellow Eyes enters the room, in pursuit of Syd as a frightened David stands helpless.

And just as it seems like David Haller's topsy-turvy world is beginning to make sense -- he's a powerful mutant who plays a host the consciousness of another powerful, evil mutant, who mucks with his memories -- "Legion" throws us another twist: Syd is transported, presumably by David, to Clockworks Psychiatric Hospital, where they're participants in group therapy alongside Melanie, Ptonomy, Cary, Kerry, the telekinetic guy and The Eye, with Lenny as the psychiatrist. Is this a creation of David's mind, or of the Devil's mind? Or has it been the reality all along?

Odds and Ends

• Notice both the tree wall mural in the white room's bathroom and the tree in the re-creation of David's childhood bedroom. Trees have been a recurring element throughout the series, from the murals and artificial trees of Clockworks to the more obvious forest settings of Summerland, "Dr. Poole's" lighthouse and even Division 3's bunker.
• Interestingly, Syd ditched her signature orange on a couple of times in this episode, most notably when she and David were dressed in white in the white room. However, after returning from that first surprise visit, she and David were both clad in black, which may be indicative of their closer bond. This was when she seemed oblivious to the radical change in David's behavior, and was willing to go with him to rescue Amy. After he set off alone, Syd donned orange again.