A sudden moment of inspiration:

The Dark Jungle

The Dark Jungle is a demiplane of the Spiritworld that connects to an area in the eastern reaches of the Mahiri Jungles.

The Dark Jungle is a large valley surrounded by steep hills and clifs, entirely covered by tropical trees, ferns, and vines. The valley can only be found without magical help at night when the sky is completely black and no moon is out. During these times it is impossible to tell the boundaries between worlds and most people who travel through the remote region set up camp before nightfall and will not leave their fire until dawn. Inside the Dark Jungle, there is no day and night, only the stars in a perfectly black sky without any moons.

The Dark Jungle is the domain of a demigod naga said to appear as a gargantuan black snake with obsidian scales and the face of a dark elf. She is worshiped by some naga sorcerers but does not have any minions of her own in her realm. However, there are all kinds of reptilian beasts making their home in the valley, preying an smaller animals that have found their way inside the Dark Jungle during starless nights, and the ocasionall unlucky wanderer.