WARNING: This article contains some light spoilers for the film "Doctor Strange," now in theaters.
As you may know by now, the Sorcerer Supreme's longtime foe Dormmamu is introduced in Marvel's "Doctor Strange" as the secret "villain behind the villain" at the end of the film. Naturally, viewers might be thinking, "OK, but who is Dormammu?" So we're here for you!
Dormammu is probably Doctor Strange's greatest enemy, but amusingly enough, the first time his name was mentioned was in "Strange Tales" #115 (Doctor Strange's origin, by Steve Ditko and Stan Lee), when he was called on for help!
You see, when the "Doctor Strange" feature began, Doctor Strange and his mentor, the Ancient One, both practiced so-called "black magic," so even though they were good guys, they would call upon dark forces to perform their spells (so did the evil Baron Mordo, who was the Ancient One's top apprentice before Strange came along). Thus, for a year or so, Dormammu existed only as part of invocations that they would all use. This was all part of the fact that Stan Lee was just coming up with essentially gibberish for the invocations, just making up cool-sounding names on the spot. Then, either Ditko (or later writers on the series) would look at the names and then come up with backgrounds to fit those names. For instance, in "Strange Tales" #116, Strange invokes three beings, none of which we knew anything about at the time...
All three beings (Agamatto, Dormammu and the Dweller-in-the Darkness) would later be written into the "Doctor Strange" comic book series.
Finally, in "Strange Tales" #126 (by Ditko and Lee), the Ancient One informs Strange that Dormammu is planning on leaving the Dark Dimension, so Strange heads off to try to stop him, despite the warnings about how powerful he is...
This is around the time that Ditko really got into exploring other magical dimensions as the series got more and more trippy. The early "Doctor Strange" stories were fairly restrained and succinct, but now they were beginning to get more sprawling as Ditko explored longer story arcs. In the Dark Dimension, Strange met a young woman who tried to warn him away from challenging Dormammu. Strange was undeterred and he met Dormammu for the first time, although Ditko's classic visual was not yet in full bloom...
That storyline also introduced the Mindless Ones, beings who were also in the Dark Dimension. Doctor Strange actually came to a truce with Dormammu in that first storyline when he helped Dormammu stop some Mindless Ones who had escaped their prison and were about to kill the mysterious woman, who Strange did not yet know was Dormammu's niece, Clea..
Dormammu wasn't gone long, as he soon returned as part of one of the most epic storylines of the entire Silver Age, as Ditko plotted out a massive sixteen part story where Dormammu and Baron Mordo teamed up, with Dormammu increasing Mordo's powers so that he could defeat Strange.
During this story, Ditko revealed the more traditional flaming head design for Dormammu and in "Strange Tales" #141, Strange even defeated Dormammu in combat!
This, though, led to the epic conclusion in "Strange Tales" #146 where Dormammu's ultimate plot was revealed - he wanted to usurp Eternity itself! This was Ditko's final Doctor Strange story and it was magnificent.
We later met Umar, Dormammu's twin. You see, Dormammu and Umar both came from the Faltine dimension, a dimension consisting of energy beings. Umar and Dormammu were mutants, in their own way, as they wanted to have physical form. So they were banned to the Dark Dimension, where they eventually conquered together, with Dormammu reclaiming part of his past heritage by embracing the flames of regency around his head. Clea is Umar's daughter.
Dormammu's next appearance featured a clever resolution. Dormammu had vowed never to go to Earth, so Strange tricked him into breaking his vow, which caused Dormammu's own power to turn on himself.
His next big storyline was the classic "Avengers/Defenders War", where Dormammu and Loki manipulated the Defenders and the Avengers to fight against each other, with the ultimate plan being Dormammu and Loki (but really Dormammu, as he knew Loki would betray him so he betrayed him first) getting the powerful Evil Eye. Dormammu took on the combined might of the Defenders and Avengers!
Eventually, Scarlet Witch was able to use a hex to stop the dreaded Dormammu. This caused Dormammu to try to kidnap her during her wedding to Vision, but he is thwarted again.
Due to his vow not to interfere on Earth, Dormammu mostly had to work behind the scenes throughout the 1970s-1990s, although at one point he actually possessed Doctor Strange's own body to try to work around his vow!
Perhaps his next major arc was in, of all places, a "Hellcat" mini-series by Steve Englehart and Norm Breyfogle, where Hellcat has to stop a plot by Dormammu to take over hell itself by aligning himself with a few "devils" against Mephisto! Hellcat had to work alongside Mephisto to stop Dormammu's plot.
Dormammu next tried to attack Earth in "Amazing Spider-Man" #57-58 (by J. Michael Straczynski, John Romita Jr. and Scott Hanna) by tricking the superheroes of Earth to drawing him to Earth themselves, thus getting him around his vow. He succeeded and was going to destroy everything in his wake...
The only way Strange could stop him was to send Spider-Man back in time to stop the heroes from falling for Dormammu's trick, but that meant Spider-Man pretty much having to relive his whole life again (in "Amazing Spider-Man" #500) and resist changing anything else.
Most recently, Dormammu used his brilliance as a behind-the-scenes motivator to help empower Parker Robbins, the Hood, in an attempt to get Robbins named the new Sorcerer Supreme after Doctor Strange lost the title. Here he is in "New Avengers" #51 (by Brian Michael Bendis and Chris Bachalo)...
Since he can't actively show up on Earth, Dormammu is often out there trying to conquer other dimensions or working other long term plans. One of the scariest things about Dormammu is his patience. He doesn't care how long a plot might take so long as it works, so he's always someone that you have to look out for.
Now that Doctor Strange has been severely weakened in his current ongoing series after the Empirikul destroyed much of his magic, it is only a matter of time before Dormammu tries to take advantage of Strange's relative weakness. Plus, of course, we'll see him more in future "Doctor Strange" cinematic stories - could Dormammu and Thanos work together? Perhaps against each other? It will be fascinating to see where he goes next.