Guiltythree
Interesting thought, so we know that the dream realm is an amalgamation of various realms spliced together and that nightmare creatures are just corrupted beings, so that means that the nightmare creatures, in all of their variety, are just the previous past species of those realms. Considering this and how people like wing flower had their worlds spliced with the dream realm, why haven't we seen a single nightmare creature that resembles a human?
we did ... like alot actually. the carapace centurion for example, the description of the memory that sunny got when killing them early on, his Jade sword I think it was, talked about how they used to be a military force of the people of this land. or more recently in Antarctica, the scavengers that fiend used to be, they are all kinda human like at first. Corruption just mutates everything beyond recognition.