Yeah, Castlevania makes itself out to be demonic and magical (all those glyphs and stuff), but the series, especially IGA's games, are clearly influenced heavily by H.P. Lovecraft and colleagues. The Mythos is full of alchemy and said glyphs were alchemic in nature as well. You have gravediggers (granted, that was based on The Undertaker), The Creature, hunchbacks/Igors, some things that were possibly based on The Hound (a Lovecraft story about a demonic dog that terrorized a couple grave robbers), the various laboratories, the lower castle levels with glyphs and runic symbols, and a bunch of other things I'm probably overlooking. Sure, IGA included witches in his games and Dracula was referred to as a sorcerer, but Castlevania is clearly an alchemic creation. Oh! The crystals that bosses drop. I'm almost certain that's alchemic in nature, kinda like the Philosopher's Stone. They actually will play a significant role in the stories of my games (planning on making more than one if I ever stop hacking and get back to programming).
I'm glad I'm not the only person that noticed the doctors in House always think it's Lupus.