The White Walkers are the most mysterious entity in the Game of Thrones universe. While we understand where they come from, and what they seem to want (i.e., to turn the living into undead), we don’t really understand why. At the heart of this mystery is a pattern the Walkers create, a swirl, which we got our latest glimpse of near the end of the season 8 premiere.

[Ed. note: This post contains major spoilers for Game of Thrones season 8, episode 1]

In the first episode of season 8, we see the most haunting swirl yet: a collection of limbs ... and Ned Umber at the center. Tormund, Beric, and Edd discover the swirl, and Beric quickly gives us a glimpse into what the spirals might be. He explains that they’re a message from the Night King. But, before we have a chance to learn any more, Ned’s small corpse comes back to life and interrupts any further insights.

Chronologically, the first appearance of the spiral comes when the Three-Eyed Raven shows Bran the creation of the White Walkers in the season 6 episode “The Door.” Just before the Children of the Forest plunge a dragonglass dagger into a man’s chest, the camera pans up, and we see that he’s tied to a tree at the center of the now-familiar spiral pattern. From then on, we see the symbol pop up when large groups of White Walkers show up, especially when they kill things.

The earliest example of the mysterious visual popping up in the show’s actual run happens in the very first episode, when White Walkers kill group of wildlings and arrange their mutilated bodies in a pattern.

The symbol also pops up in season 3 episode 3, when Jon revisits the Fist of the First Men and sees that the Night’s Watchmen who were killed there have disappeared — and all that’s left are pieces of their horses in a spiral.

The symbols also appear deep in the dragonglass caves of Dragonstone, in season 7, episode 4, “The Spoils of War.” According to Jon, the Children of the Forest carved these markings in memory of the battle they fought alongside the first men to defeat the White Walkers ... the first time.

What exactly these shapes represent to the Walkers, or what purpose they serve in the world of Westeros, are questions fans have been trying to answer for years. Some theories see them being associated with the particular flavor of magic associated with the White Walkers’ creation. One fan theory suggests that the markings could simply be a kind of reminder to the Children of the Forest and the first men that the White Walkers haven’t forgotten how they were created. Another theory posits that creating these symbols out of bodies could be somehow tied to the weather. The further south the White Walkers create the symbols, the further south winter can move.

In one post-episode interview, co-showrunner David Benioff explained that these patterns were originally created by the Children of the Forest, and had a mystical significance to them. Since then, they’ve been co-opted by the White Walkers. So it’s entirely possible that they are a means of communication, or a perversion of certain important symbols from their creators.

Ultimately, the answer to what these spirals are may never be solved. They might be one piece of the puzzle Benioff and co-creator D.B. Weiss will leave to their ultimate master: George R.R. Martin. Or they may be even less “important” to the larger narrative. If the Night King’s army is a parallel to natural catastrophes exacerbated by mankind, the swirls may be analogous to the weather patterns we see so often on TV — the unimaginable geometry synonymous with destruction.

The only ones who can truly tell us are the White Walkers themselves, and, well, they don’t seem very talkative.