As I specified in the presentation thread, Im making a campaign for a tabletop RPG named "The legend of the 5 rings", a game about samurai and bushido, in an "emerald empire", cross of mythical Japan with a few touches of ancient China, Korea and Mongolia, with heavy supernatural presence. (To the people who knows the game, the setting i'm going to use include a defeated Fu Leng, so the presence of Jigoku in the empire is heavily diminished.)

Is In this case, i'm making an adventure where the players must face a great "Alchemist" who wants to become a new "Jigoku Lord" gaining power and inmortality this way. I remember a story I read or see when I was a child, where to get this goal, the "magician" have to drink demon blood or kill thousands of people, but the details have long ago sliped from my brain.

So thats my question: someone could indicate me to some legends related whit this, with the idea of becoming a demon, oni or a youkai through alchemical rites or the like? To make this antagonist really strong and firmly based on some real tradition would be a really great achievement for the story as a whole.

Thanks and great day!

Well, I'm not particularly familiar with this one, but there is in fact a saying that upon killing a thousand demons (metaphorically being bathed on their blood) you would become a demon.
I think I've read about other many ways of actually gaining power becoming a proper demon (as in, from Jigoku, not just a youkai)... but it's a concept that's too mixed around in many cultures and fiction that I can't tell anything for sure.
Probably there are many rituals of this kind... but yeah, I've never looked up into any real ones.


Also, many youkai tales are that of former humans (most youkai were former "ordinary" creatures anyway, humans are no exception). For instance, the futakuchi-onna was once a woman who developed a second mouth, so you could look up on individual humanoid youkai. Most of them don't seem to be voluntary transformations though... One particular voluntary one could be the Bridge Princess (Hashi Hime), who decided to become a youkai out of jealousy and vengeance doing an specific ritual.
Voluntary or not, most human transformations into youkai come mainly from a particular strong emotion. Some tales talk about rituals, but others don't.

... I'd really like to give you actual sources like books and such, but to be honest I don't really know any... ￣×￣；；

I agree with Shii-chan, and have a bit more to add.

Normally, in Japan, if someone wanted more power, they would want to become a kami (god), rather than the ruler of Jigoku. Also, I believe Jigoku came from a Chinese idea (loosely based on Buddhism/Taoism?), so I don't think Japanese myths/culture/etc. can help you with that. Honestly, I haven't found much mention of "jigoku" in my readings, but this might be (if it is connected to Buddhism) because I don't focus my readings/research on Buddhism much. Yomi, however, the underworld, is hard to explain, but a place of inpurity that no one (human or otherwise) really wants to go to. This is the only similar thing I can think of...
In some Japanese stories I've read, they want to become kami, or they've turned into an onryou or the like to extract revenge - this being the more common. Like Shii-chan said, it's based on strong emotion for the most part.
The killing of thousands of people is probably quite accurate - that you yourself become "something" of a demon, probably innocent blood, not blood split on the battlefield, and I'm sure that's come up more than once. I suppose making a deal with demons would work, though - the only thing I can think of is "Dororo", which is a fictional manga/movie.

As for the Alchemist thing, I wondering what you're refering to, as Alchemy in the western sense isn't native to Japan. If you're refering to Onmyouji (which is the closest thing), then I suppose you can work with that, but it would go against the principles of Onmyoudou (which I suppose would work for this sort of character). Perahaps ask one of the others about that though, my brain's not working in English at the moment.

As for actual legends, I'm pretty sure there aren't any along these lines. I'll keep looking, but I've never come across something like this. This sort of dynamic (? for lack of a better word) isn't common to Japanese culture.
Perhaps you should look into the Chinese-side? - jigoku doens't have much weight in Japan from what I know.

Thank you very much. If don't point exactly to what I'm seeking, at least your incadications help me to narrow the field. For what you say, I'm mostly sure now the story I saw was on the more popular culture side of the legendary, not so in the really traditional, so I can keep investigating that way.

When I say "alchemist" i'm talking mainly about te idea of gaining inmortality through "magical" substances and rites, a concept typical in Chinese culture, and probably inherited in some way to Japan. All the magatama and related magics.

Efectively, all this idea seems to be more related to confusianism and buddism than Shinto, so the "demons" I talk about, are more close to Oni than Youkai.

Jigoku is the japanese version of Chinese Diyu, basicaly, "Hell".The goal of the antagonist isn't to go into the hell, anyway, but to merely gain power though "hellish" methods. Maybe there are some legends about diabolic contracts or the like?

Thanks again for the information.

By the way: How do you become a Kami? Maybe thats a better aproach for the character: a Kami related to negative concepts could be as useful as a demon to my story.