The Trailer For Frozen 2 Left Us With a LOT of Questions — Here Are Our Theories

At the end of the trailer, Elsa uses her magic to clear away a mystical fog and reveal four standing stones that are strikingly similar to the Celtic shrines from Pixar's Brave. Each stone bears a rune like the ones on the diamonds Elsa created before, so there's definitely a connection there. Does that mean that whatever is in the Great Unknown influenced Elsa to somehow create the runes, or was it a sign of things to come?