User blog comment:Hitsuji Mamoru/Servant Creation Room 2 : Guess of the Who/@comment-4802891-20170526200433/@comment-4802891-20170607163533

It's not a cauldron but you are thematically  on the right track.

Seeing how hard it is, I'm going to have a small info : the fiction is not as old as something like Frankenstein, Sherlock or Jekyll.