Thomas also tells Anton that the seventh level of the Twilight is the Others' paradise, where they can exist in peace together (upon death, Others just vanish into the Twilight). Merlin has hidden the Crown of All Things in the seventh level of the Twilight.
In that mysterious place Merlin apparently hid the "Crown of All Things" (nobody knows what it is). After the Night Watch is attacked by ordinary humans equipped with magical amulets and bullets, Thomas and Anton follow someone to the Twilight.