Game of Thrones Season 8 opened with an episode that loudly called back to how the show originally began. The pilot for the series is famous, partly because it was filmed twice when the first one didn't screen well. However, while it rarely makes critics' lists of Game of Thrones' Top 10 Episodes, it has many iconic moments, all of which were called back to in the Season 8 premiere. The most violent callback was undoubtedly the symbol around the Umber boy in Game Of Thrones, in a scene that reflected the show's original cold open.
In Game of Thrones Season 1 Episode 1, three Night Watch members go out ranging beyond the Wall. The youngest, Will, finds a strange sight: Bodies, arranged in a mysterious pattern, with a dead wildling child above them, nailed to a tree. By the end of the scene, that child is no longer hanging from the tree, but up and walking around ready to kill.
In Game of Thrones Season 8 episode 1, Wildling survivors are now below the Wall, when they come upon a band of Night's Watch from Castle Black. The group has found a strange sight: Bodies, arranged in a mysterious pattern, with a dead Northern child in the center, nailed to the wall.
But the pattern is one fans will recognize now, a decade in.
From Game of Thrones Season 3, when Jon stumbles across the Fist of the First Men, and the Night's Watch who were there are gone.
Obviously, it's both a message and a warning. This is a place the White Walkers have killed, and this symbol commemorates their victory. It's also a warning, but less to the men that find it and more to those who made them in the first place.
From Game of Thrones Season 6, the above view of the scene where the Children of the Forest make the first White Walker fighter by inserting dragonglass into his heart:
Whatever magic the Children used to create the White Walkers, this symbol was part of it. Fans know this because that exact spiral drawing appears in the caves under Dragonstone, as part of the pictures telling the story of the first Long Night, and warning of the Night King and White Walker menace.
It's notable that the first pattern fans saw, way back in Season 1 episode 1 actually wasn't the spiral, but the other symbol White Walkers make. However, like the spiral found in the Season 8 premiere, body parts were used in the same fashion, with a child hanging over them.
Much like the wildling child in the pilot episode, the poor Umber boy (whose name is Ned, by the way) also comes back to life, ready to kill.
But unlike the pilot, Tormund and Beric are experienced enough to be able to interpret the message. While the spiral is still mysterious, they understand what the White Walkers are saying just fine. The Army of the Dead is between the Wall where they are and Winterfell. Any attempt to cross the line will be unsuccessful. The only hope Beric and Tormund have now is to ride around the Army and down to Winterfell to warn the Starks before it's too late.