Abyss, The

From Srafopedia

The Abyss is a great mystery in HDM. Opened by the bomb that the Magisterium uses to try to kill Lyra, it is probably a place between the borders of the worlds and “fills up” the space between. Metatron, Lord Asriel and Mrs. Coulter fall into the Abyss during a struggle in the final confrontation. Dust will constantly leak into it until it is finally gone. Therefore, the leaks must be closed by the angels. Leaks are caused when great energies are released, for example, when an individual is severed from their dæmon, or when The Subtle Knife is used to cut a hole into another world.