We know a few key details about Shadow of the Erdtree's setting - it's around the size of Limgrave, is separate from the existing map, and is accessed via Miquella's cocoon in Mohg's boss arena. But as for where it tangibly exists... that's still a mystery. However, Elden Ring sleuths are hard on the case and think they've cracked it.
In the base game, six divine towers surround a huge empty area of the map where a cloud ominously looms overhead. There has long been speculation that the towers' placement holds some unknown significance, and the trailer might have proven just that. The sky in Shadow of the Erdtree is masked by an enormous ethereal black veil that is, coincidentally, made up of six drapes.
Alltheheroesaredead suggested on the game's subreddit that these drapes could be held in place by each divine tower, hiding the Land of Shadow. The empty space would fit a landmass the size of Limgrave and a magical veil would explain why it looks like part of the ocean from the outside. It certainly fits, but there's even more evidence to support this theory.
"It's no secret that Marika has a proclivity for hiding things - about herself, about others, about events," Alltheheroesaredead wrote, comparing the veil to Marika's bed chamber. "There is no limit to what she is willing to do to maintain the illusion of her order. The Mimic's Veil, also known as Marika's Mischief, allows one to change their appearance to something inconspicuous. It's widely accepted that this is an artefact that once belonged to Marika - seemingly pilfered by Godrick from the capital when he was forced to flee.
Elden Ring fans also theorise that Messmer, the red-headed villain headlining the DLC, is brother to Miquella and Malenia , making him a child of Marika.
"I think the grand sort of baldachin fabric we see draped in the sky of the DLC could be tethered to the divine towers to create a sort of magical canopy—unfurled spools of the concealing veil fabric the Black Knife Assassins
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