Avengers: Infinity War secretly referenced the X-Men villain Juggernaut thanks to Doctor Strange's mystic powers. The battle between Thanos and Doctor Strange was one of the highlights of Avengers: Infinity War. Strange had foreseen the team's defeat, but he knew what he had to do to make sure they could win in the future. As a result, he levied some of the most powerful spells seen in the MCU to date against the Mad Titan. It was the ultimate "Wizard's Duel," with the power of the Sorcerer Supreme pitted against the near-complete Infinity Gauntlet.
Marvel explored a whole range of ideas; concept art has shown Strange sending Thanos across the dimensions, mirroring the "Magical Mystery Tour" in Doctor Strange. But it turns out the final version had some pretty impressive deep cuts into Marvel lore - and even subtly referenced an X-Men villain. At one point, Strange uses a spell that pins Thanos with extradimensional energy. On Avengers: Infinity War's commentary track, Stephen McFeely asks, "Are those the Bands of Cyttorak that we decided?" In response, Christopher Markus says, "Those are the Crimson Bands of Cyttorak." This is actually something of a retcon - Marvel had previously described a restraining device that held Kaeculius in Doctor Strange as the MCU's version of the Crimson Bands. But it's also important because it incorporates an X-Men villain into the MCU, and potentially even has implications for the future of Marvel's shared universe.
In the comics, Cyttorak was a powerful demonic being who was worshiped on Earth, until he was banished from this dimension in unknown circumstances. The monstrous being took up residence in the so-called Crimson Cosmos, and offered his magic to worshipers such as Morgan Le Fey. Cyttorak's cultists successfully created the Crimson Gems of Cyttorak, mystical gemstones through which Cyttorak would choose his "avatars." These avatars became known as the Juggernauts, and their task was to bring glory to Cyttorak's name by wreaking havoc and spreading destruction. The most famous of the Juggernauts is Charles Xavier's step-brother Cain Marko. He's a classic X-Men foe, and a comic-accurate version of his Juggernaut appeared in Deadpool 2.
In Doctor Strange, the Ancient One explained how the MCU's model of magic works. "The language of the mystic arts is as old as civilization," she explained to Stephen Strange. "We harness energy drawn from other dimensions of the multiverse, to cast spells, conjure shields and weapons to make magic." That neatly explains the Crimson Bands of Cyttorak; the spell Strange has learned taps into Cyttorak's power, drawing energy from the Crimson Cosmos, and uses it to create what would ordinarily be an unbreakable restraint. Of course, even the power of Cyttorak failed against the might of the Infinity Gauntlet.
The implication of all this is that Cyttorak exists within the MCU, most likely in a comic-accurate form, and as such he has the potential to be a major player in the MCU's future. In the comics, the worship of Cyttorak was particularly common in the days of Camelot and King Arthur, with Morgan Le Fey serving as a Cyttorak cultist; there's some evidence The Eternals may actually be visiting Camelot, while Morgan Le Fey herself will make her small-screen debut in Runaways season 3. Meanwhile, Doctor Strange 2 promises to explore the Multiverse, and there's speculation the fabric of reality itself will be torn apart in the MCU's Phase 4. If that is indeed the case, Cyttorak could make his presence felt - and perhaps even choose the MCU's Juggernaut.
