Sonic the Hedgehog 4will introduce Metal Sonic as its next big villain, but theKnucklesTV show proved it also has the perfect antagonist for Shadow.Sonic the Hedgehog 3’s post-credits sceneintroduced Metal Sonic, a powerful adversary who, in the movies, sports an army of other Metal Sonics who attacked the Blue Blur. Luckily, he was saved when Amy used her Piko Piko Hammer to destroy them, laying the groundwork forSonic the Hedgehog 4’s story. Based on both characters' debut,it seems like their first game,Sonic CD, will be a major inspirationfor the next movie.
However,Paramount’sSonic the Hedgehoguniverse hasn’t been adapting the games directly, taking plenty of liberties with the stories being told. This includesKnuckles, which saw Pachacamac debut as the echidna’s spirit guide, very different from his role in flashbacks during his debutSonic Adventure. It’s these alterations that make the movies unpredictable, as it’s never clear when a new element of the franchise will debut. However, onecharacter inKnucklesmay have confirmed Shadow’s next adversary, who could show up inSonic the Hedgehog 4.

Sonic The Hedgehog 3 Confirms A Subtle Shadow Reference Was In Knuckles' TV Show
Sonic the Hedgehog 3 finally properly introduces Shadow the Hedgehog, but his origins were already teased in the Knuckles spinoff series.
Knuckles Introduced Iblis Into The Sonic Movie Universe
The Fire Demon Comes From A 19-Year-Old Sonic Game
Knucklesepisode 4 introduced the Fire Demonwhen Wade experienced the title character’s backstory through a rock opera dream. In the episode, it’s revealedKnuckles defeated the Demon and stole his power, that power being the Flames of Disaster. It allows the echidna to coat his fists in fire, something shown both in the series and during the events ofSonic the Hedgehog 3. While the Fire Demon shows up in puppet form with its eyes and mouth glowing red, a painting of it on a sign shows it with green eyes instead.
This painting makes it look like Iblis, a fire demon introduced in 2006’sSonic the Hedgehog. In the games,Iblis is a powerful fire monster whose devastation results in a cataclysmic future. He’s even referred to as the Flames of Disaster, with Knuckles' new move clearly being named after him. While his new connection to the echidna warrior meansKnucklesseason 2could delve deeper into his power, Iblis actually has deeper ties to anotherSonicvillain. Who, in turn, has a backstory that’s directly related to Shadow.

Iblis Is Connected To Mephiles The Dark, A Major Shadow Villain
Mephiles Is Shadow’s Shadow
InSonic the Hedgehog2006, Iblis is one half of the sun god Solaris, a powerful entity worshiped by the people of Soleanna.His other half is Mephiles the Dark, who first appears breaking free of the Scepter of Darkness near the start of the game. He ends up taking on the form of Shadow’s shadow, acting as a dark opposite to the hedgehog with his own schemes for world domination. He wanted to release Iblis, who was sealed away in Soleanna’s Princess Elise, and fuse with him so they could become the unified Solaris once more.
[H]e returned inSonic x Shadow Generationsas a boss, attempting to become real once again, still having knowledge of the events of his game.

Later in the game, it’s revealed theSonic the Hedgehogvillainwas originally sealed away by Shadow, who traveled back in time with Silver the Hedgehog, successfully creating a time loop. This is why he began targeting the Ultimate Lifeform after he was released, tormenting him by claiming in the future, humanity would betray him. He was ultimately extinguished from history by the end of the game, erased from everyone’s memory in the process. However, he returned inSonic x Shadow Generationsas a boss, attempting to become real once again, still having knowledge of the events of his game.
How The Sonic Movies Can Introduce Mephiles
His Time Travel Origins Could Be Revealed In Sonic 4
If Mephiles' backstory remains tied into time travel, thenSonic the Hedgehog 4’s storycould connect him toSonic CD’s Time Stones, time travel objects used in Amy and Metal Sonic’s debut game.This would help bring Shadow into the story by establishing Mephiles as a major antagonist, using similar ideas from the 2006 game to establish their connection. However, with Iblis' backstory drastically changed, the same might be done for the shadowy entity. This would keep him connected to Shadow without forcing the Fire Demon to reappear, a change that could better focus their conflict.
Although Mephiles isn’t going to be the main villain ofSonic the Hedgehog 4, the sequel’s potential time travel elements could lay the groundwork for his movie debut. This would offer a strong start to his battle with Shadow,potentially setting the stage for a spinoff starring the Ultimate Lifeform, or anotherSonic the Hedgehogmovie with him as the central antagonist. With Iblis already in the movie universe, it’s only a matter of time before his darker half arrives to cause chaos.

Producer Toby Ascher has confirmed plans for moreSonic the Hedgehogmovies and TV spinoffs in the future.