Unfortunately, it seems that I'll have to tweak one of the latter's summons a bit, since sapient extradimensional living jack-o-lantern that shoots fireballs seems unlikely to be acceptable.
I was going for more of a Cthulhu-mythos take on weird stuff like that where it's more underlying our own reality, but I kind of figured. ^^;
Actually, I am allowing a 'spirit world' in the sense of an 'unseen layer' coinciding with the physical world that some people are sensitive to, especially magic users or psychics. People with such sensitivities may notice the three great abomination-like presences observing the planet. And your sapient Jack-o-Lantern idea is fine as long as it's explained as starting out as a simple magical construct that was capable of following simple commands, that over time started to develop free will, or something like that. As long as it's not something that already existed, and came over from another dimension saying, "There are plenty of us on the other side, and we're all quite mad over there," or anything like that. I hope my restrictions and allowances are making sense and are creating a sort of cohesive framework that you all can work off of. Non-human sentients can exist as aberrants or rarities; usually constructs, artificial intelligences, or unusually long-lived natural or magical creatures; things that exist so few and far between and so disparate from one another that they cannot come together and form their own society. And nothing that could be interpreted as definitive proof of dieties. magical items from myth can exist, since you can't prove they were actually made by gods.