Glistening in the light of Acheron, the crystalline structure of the Atrium is a fragment of Earth, carried across the void; a snapshot of green and blue amid the pale tans and reds of Tarterus, a promise and a dream.
During a storm the PCs come upon a little boy that plays in the rain. Upon further inspection they discover that he has one eye and a long tongue lolling in its mouth. Spit dripping. It is a demon from beyond that can access our realm during storms, it eats all heads that are not its own, living and dead.