Neither are his brass knuckles
The first lesson Strange learns under the Ancient One is how to open up portals to travel to different places on Earth or other dimensions using a device called the "sling ring." You might have to be a psychedelic 1960s cartoonist to come up with a shiny hand ornament that focuses brain energy, but surprise: It's not from the comics. Director/co-writer Scott Derrickson said, "The gateways, the forming of the gateways that are used for that, that's straight out of the comics. I just needed an object for them to carry it on." There's never been anything exactly like the sling ring in comics. The closest thing (which is still a stretch) is the Wand of Watoomb, which opens portals to other dimensions, among many, many other things.
Because you can never have enough universes…
There have been so many dimensions introduced in the pages of Marvel Comics that they can be hard to catalogue and remember. One is the "Dark Dimension," which makes a brief but pivotal appearance in the movie. Introduced alongside our sorcerer hero in the 1964 issue of Strange Tales, the Dark Dimension is home to Dormammu, who usually inhabits the throne when not battling his sister, Umar, for it. Dormammu is hell-bent on seizing other dimensions to add to his realm… which is actually pretty similar to what we see in the film. Dormammu isn't a demon, exactly, but a Faltine, an extra-dimensional being born from pure magic. One of the oddest Dormammu appearances comes in the bad mini-crossover Ultimatum, in which he squeezes Strange so hard his head pops off. Which is kind of similar to how I used to play with my Barbie dolls as a kid. It's as gruesome as you think. Thankfully, this was in an alternate universe.