Even though both the books and their film adaptations concluded years ago, Harry Potter fans are still regularly coming up with theories about the Wizarding World. Some could change the entire understanding of the series, while others, like this Dark Mark hypothesis, simply add an interesting dimension to the details of the story. This particular theory has cropped up a few places before, but it was Reddit user Galaxy3110 who recently realized the connection, and posted it online. In a r/harrypotter post, they wrote that "Voldemort modeled the Dark Mark off Salazar Slytherin's statue in the Chamber of Secrets." Users replied to state that it was a neat connection that they hadn't noticed before, and the evidence — as seen in the picture above — speaks for itself.

As a refresher: In his second year at Hogwarts, Harry visits the Chamber of Secrets, an aptly named secret chamber under the school that was created by one of the school's founders, Salazar Slytherin, to house a basilisk. When Harry tries to save Ginny Weasley from Tom Riddle, the giant serpent dramatically slithers out of the statue's mouth, much like the snake in the Dark Mark does. Since Slytherin clearly had a love for theatrics, it's easy to also imagine the basilisk emerging from his mouth like a murderous tongue as a symbol for his own ability to speak to snakes in Parseltongue.

Voldemort, as we find out, is both a Parselmouth and the Heir to Slytherin, so it would make sense for him to take inspiration from the imagery of the basilisk emerging from the Slytherin statue. Plus, when the Dark Mark is cast as a spell into the sky, its green color could be in reference to the Slytherin house color (which has its own hidden meaning). 

Since Harry Potter author J.K. Rowling has revealed all sorts of details about the Wizarding World after the books finished, it's possible that she might confirm this theory at some point. Even without that, however, it's fun to imagine Tom Riddle standing in the Chamber of Secrets, sketching out his edgy tattoo idea.