small castlevania: curse of darkness headcanon i've been meaning to share:

i 100% believe hector and isaac collaborated on their innocent devil designs, which accounts for the variety you see in-game (and why they both have the same IDs in their arsenal, game logic aside)

but individually, they both have a very different approach to ID designs

isaac is from an accomplished family of sorcerors, steeped in knowledge of the dark arts since he was born. so it makes sense his IDs end up looking way more demonic and hellish, terrifying creatures that in no way resemble anything made by God. and y'know, it really just suits his whole edgy aesthetic lmao. but as a point of reference, his designs really lean into reptilian, draconic, or insectoid forms for all those angular shapes and otherworldly qualities. there's nothing soft or nice about them (but def have that "face only a father could love" vibe going on)

hector, on the other hand, has a fondness for animals, especially creatures of the night, and so his IDs are made in their image. but since so many of his animal companions as a child were chased away or outright killed for the crime of providing companionship, his IDs are made bigger, stronger, and more terrifying so no one would ever dare harm them, or him, again. leans towards the more mammalian side of things - recognizable as animals albeit very fucked up since he likes to mix and match characteristics