It was really exciting to respond to those comments on designing languages, and I'm always open to more discussion of questions, but tonight I want to do something different. I'm going to talk about Japanese ghosts and spirits.
This list doesn't include dragons, which I guess fall into their own category. But the ghosts do include creatures like the tengu, a goblin creature that is both birdlike and manlike, and can change its form into that of a wandering priest. Then there's the kitsune or fox, who can change its form and appear to be a woman (sometimes with a tail). The tanuki (roughly translated as raccoon-dog) is a mischievous creature and can change its form as well, as can the scary bake-neko or ghost cat. In fact, obake-mono translates literally as "change creature."
A noppera-bo will appear to be someone so upset that they are hiding their face, but when they finally turn to you, you'll discover they have no face at all, but a smooth egglike complexion. The rokuro-kubi seem normal by day, but at night their heads fly off their bodies and make mischief, sometimes attached to the body by a long rope of flesh!
These are some of my favorites, but I couldn't possibly list them all here - I'll let you explore The Obakemono Project for that. What I do want to comment on, though, is the way the Japanese ghosts have characteristics that make them particular to Japanese cultural concerns.
Consider for example the laughing woman (kera-kera onna), who haunts people by laughing derisively.
Or consider the "ghosts" caused by neglect: the two-mouthed woman (futakuchi onna) which is essentially a normal woman who grows another mouth because she's been neglected; the karakasa-obake which results from the neglect of an umbrella; another which results from the neglect of shoes, and a host of other objects that take on spirits of mischief if they're left untended. There's also the tenjo-name, a creature who licks dirty neglected ceilings.
I'll close by going back to the idea of obake-mono as "change creatures." Among the vast number of Japanese cultural concepts we find tatemae (front, facade) and honne (true feeling). Different value is placed on maintaining one's polite face, and showing one's true feelings, depending on the circumstances - so it should come as no surprise that deception, change, and the revelation of the true nature of a creature would feature so prominently in the Japanese ghosts.
I'll leave it up to you to think about how our own Western ghost creatures might reflect our cultural concepts. But I hope you feel inspired to consider superstition as an area ripe for exploration in the creation of fantastical or science fictional peoples.
I've always thought that a culture's demons, devils, angels, and the like reveal immense amounts about a culture.