Strictly speaking, the name is N’Gh O’Yiehrh, and that’s as close as humanity can get to the correct pronunciation, thank God. Literally. Species that can pronounce it properly tend to develop nasty personality disorders. ‘Nega-Ohio’ works well enough as a use-name; inhabitants of it are typically referred to as ‘Interlopers,’ or ‘the Unwelcome’ if somebody’s feeling vaguely pompous.
The epithets are well deserved, too. Interlopers would like to invade, conquer, and enslave Earth, only the dimension they hail from is just a little too different from our own to let them make a proper go at it. They’ve still tried several times, only to discover each time that our native reality interferes with too many of their regular biological processes. A less malevolent species would have given up long since, but the Interlopers seem particularly determined to succeed.
Interlopers have a ‘range’ covering most of the Mississippi river valley and Appalachian mountains, although they definitely prefer the latter to the former. In the flatlands, they manifest as various cryptids, usually at night (UV light levels during the day are intolerable to them). It is unknown why they try to manifest in the open, as they are barely tangible and can barely move. Possibly it’s just bloody-mindedness, or the Interlopers are acting as scouts, or they’re doing something less comprehensible.
In the mountains, Interlopers can maintain their presence in our dimension for longer periods, and typically use that time to try to acquire human servants. They pay for services via the application of ‘sorcery,’ for lack of a better word. Interlopers can’t or won’t do very many beneficial spells, but they know any number of processes that can cause serious harm. Unfortunately, humans who spend too much time in the presence of sorcery quickly become physically and mentally warped, in increasingly unsubtle ways. Which is why Interlopers are always looking for more servants*.
But, as noted before, while Interlopers are malignant they are not powerful — at least, not on Earth. Presumably they are more dangerous in Nega-Ohio, which would probably have the same effect on humans as Earth has on Interlopers. More than one occultist has wondered if that applies to sorcery, as well. Could human Interlopers in Nega-Ohio be able to create powerful curses and entropy bombs? It’s an interesting question.
Well, it’s interesting to a certain kind of mind. One that is perhaps more likely than some to want to come to an arrangement with the Interlopers. Oh, they might not last long before their inevitable implosion, but that’s hardly any kind of comfort to their victims…
*A lightly fictionalized account of this can be found in the short story “One Other,” written by Manly Wade Wellman. Wellman was definitely familiar with Interlopers and other mythological creatures of the Midwest, and this story shows that it was either a personal familiarity, or he had access to reliable eyewitness accounts. Either way: Wellman should be considered authoritative but not inerrant on the topics of modern cryptozoology and apotropaic rituals.