This post kinda exists because of discourse around the DMC show but also a bit of a sequel to something I wrote about Orcs:
https://eyeballtank.newgrounds.com/news/post/1514841
https://eyeballtank.tumblr.com/post/770234000533061632/the-discourse-around-orcs-and-evil-races-in
I think "humanlike" demons in terms of personality/look can be justified with stuff like:
* Them being the rare exception, while other demons are either pure evil or weird looking
* Or maybe if they're "charmed" or affected by someone from the outside
* Maybe if they're half-demons
* Or were humans once or use something human like a human soul
* Or even if they're pretending to be human to misguide/trick humans
* Or you could have "royal demons" that have more complex personalities while lower demons are the beast like ones, maybe
But naturally, demons are more interesting when they look weird/surreal/strange/maybe even "symbolic", have their existence tied to a symbol or some concept or even have weird limited "personalities" like not feeling sympathy or emotions.
Because demons are technically creatures of evil in some works and stuff.
They're in some ways, different from aliens and even most fantasy creatures because a demon can be more than a creature.
Even if a demon has human features in terms of looks or character, there's still something weird about them, as if their nature defies the nature from other worlds.
Aliens and even fantasy monsters can have their own form of nature because nature just is.
Like how their biology works because nature is natural, so there's no "strings attached".
Demons however can have a whole different set of rules, if any.
And it's as if the mere rules themselves have a "mind" of their own (This is partially because of who creates them, like Satan or some other powerfull entity having something in mind with how demons work and what to do with them; Because with our world for example, some would assume that God just created the world as is and left, leaving us on our own).
And how surreal a demon can look can vary, like sometimes using concepts from our world in unusual ways, like how Bosch portrayed demons using musical instruments, even in their anatomy.
This also works as a contrast to how creatures meant to be "Eldritch" or related to Lovecraft's stories are surreal in the sense that their mere visage drives you inside: Which is something that is clearly a result from literature with almost no visual reference and often associated with the typical "multiple eyes and tentacles" things that some people get tired of.
So in that regard, a demon from Hell is easier to work with than a Lovecraftian monster because one can have created ways to use some real concepts (Like most demons having horns which is a feature real animals have but then they have weird anatomy or abilities) while the other is meant to be so out-there, that it gets really lame if their tentacles remind us too much out of octopus tentacles and so on.
If I were to use my characters as examples.
In Project Nortubel, you do have demons as weird creatures like the obvious Bosch inspired monster with the yellow key or the Baphomet-like demon with an extra mouth (Based on that one painting) and the giant stone with thunder or that female head trying to mimic HR Giger's style.
Basically, I wanted to make weird characters based off some paintings and artists.
But then there's the enemies, who are pretty much souls "demonized" and turned into weird monsters.
(I think I wrote somewhere that the lanterns that chase the Companion are souls of dead childrin mindlessly trying to find a host).
With a character I revealed a while ago: Belshazzar.
I came up with a lower class of demons that is closer to humans for a reason: They're the souls of humans that "never came to be".
Basically abortion, stillborn, dead pregnant women etc.
So when a baby dies before birth, their soul is used to create these demons who are enslaved even as babies.
They do age like humans but can be a thousand years old while their adult appearences become the default.
Belshazzar is the one of these demons that breaks free from slavery and tries to find his own purpose.
On one hand, he goes to the worlds of the living to punish sinners.
On another, he goes after "escaping souls", so his interests clash against those of the 7 undead.
I guess I could also mention how Baalphomette is an anthro goat sorceress that fused with a demoness and became a half demon or the 7 undead in general (Mainly because Maikouto is an Oni which pretty much means "Japanese demon" but she's still on the same level as the rest of her group).
Another thing about demons is when they're "creatures/beasts" because something you see in a lot of games is when they're portrayed with chitin anatomy or shell-like features in them.
There are times when a demon feels a bit too close to a hypothetical animal because of how they can be designed, as if we associate art directions with "languages".
(Part of why people compare Demon Souls' original style to the remake).
With my characters, if I were to create creatures with certain chitin features, I'd probably give them to sci-fi aliens who are expected to have some marine/bug-like features while demons must try to be weirder.
(With Otulp, I have what's essentially demonic aliens, so that should be figured out too; Like establishing "rules" with the creatures from Tfoorie's world (Tfoorie being the 2 mouth, 5 eyed alien you might've seen in Nortubel) then imagining how demons for aliens would look like).
I think a reason why some demons in stuff have the chitin thing going on is because of the idea that "alien = sci-fi and demon = fantasy" and maybe because chitin is an alternative to scales, because fantasy has dragons.
Could also be because some people assume traditional demons you see in old paintings and statues are too basic.
This probably leads to some history of art styles in games that could be better studied somewhere else.
Going back to the idea of them being creatures of evil, there are settings where that doesn't always have to be the case.
But you also get an issue similar with evil Orcs where people assume a fantasy race or species represents a real group and not a concept like a disease, natural disaster or a concept alone (Like how war corrupts man).
Even if a demon isn't 100% evil, they still need a personality that makes it clear they're not the same as a human.
Don't know what else to add because I had this post in mind but didn't really expand on it while as a draft.