Nightmare Elements
by Marc Saindonthe Dimension of Nightmares is apparently the home plane for the Hin's Blackflame. so what about the other elements? If "Nightmare Air" (Miasma), "Nightmare Earth" ('Grime'?) or "Nightmare Water" ('Ichor') show up in Mystara's Prime, couldn't they serve as the basis for some demihuman relic, and if so, for which one?
For example, I could imagine Devilfish in the lightless abyssal regions near Ierendi collecting "Dark Water" for some nefarious purpose, perhaps even crafting some eerie biotech relic with the black oily substance.
maybe Miasma works like the pseudo-scientific 'Phlogiston' -- it would be innately hot, so the Nightmare Dimension's Blackflame Sun creates a zone of cold in the universe. It might manifest on Mystara in Malpheggi swamp as weird fumes alongside swamp fire and marsh gas that Lizardmen get high on to get 'inspiration' into becoming Wokani (Lesser monstrous spellcasters). 'good spots' of this marsh gas might be a resource lizardmen fight over, and why they put efforts in pushing back Azcan and Darokin to drain swamp areas for agriculture.