Exactly, just one of those odd thoughts that jump into my brain sometimes so I thought sharing it on FR might lead to an interesting answer. That way, others can ponder it with me so I don’t feel lonely...LOL!!
Actually, as I was writing this, it came to me that the pre-1914 contemporary reference might not have been an historical figure but from literature: Machiavelli’s “The Prince” could have been a colloquial reference for Rasputin-like actions and scheming. Admittedly, not a perfect fit but of a type, anyway.
I’m a big history buff, but it’s hard for me to come up with another person who held no official office or title, was not a sexual consort, and yet had enormous influence over a ruler, and all of it was bad. Given some time, I may come up with someone.