The Mists of Shadow

Comprising the Shadow Rift's actual border, the Mists of Shadow is the fog that envelops the domain. Remaining eternally closed so long as Gwydion remains trapped in the Obsidian Gate, the Mists of Shadow make a person become less and less substantial as they encroach further into the mists, eventually reaching one hundred percent insubstantial and fading entirely away forever at a hundred feet inside. At any point before then, characters can turn back and regain their former forms.