A shimmering bubble in a circle around the White Tower that sprang up after the Tower landed in the earth at the end of Season 12. Offered no physical resistance, but obscured any attempts to see or scry past it, and any who went past no longer returned, ropes cut and forces abandoned. Those who were chained and pulled back would babble vaguely about dreams and warmth.
Danica and Ethan determined to venture in, where Ethan, according to his account, was caught in a mirage of a Heaven where all those he had lost were alive, happy, and living an idyllic life, offering everything he could want.