Oh my that sounds amazing eliec. Lovecraft is by far one of my favourite authors and I have been meaning to incorporate some satanic power as the antagonist to a fantasy novel I've been working on but since that's not working perhaps it would be better fitted to an apocalypse scenario. Perhaps there is an expedition to Mars or Europa that discovers water and they bring it back, perhaps something lurks in the water that slowly infects the minds of those that are touched by it or perhaps the crew of a nuclear submarine discover something unspeakable amongst the depths of the ocean?
Sounds good to me. I'd be careful of explaining the cause too much, however. Part of Lovecraftian horror is that there is so much we do not understand, and we don't know when that will bite our collective ass.