Are you asking me? I asked the same question.
But “teacher” is only one of several roles for mentor set forth in the OP. Even the stricter definition in the American Heritage Dictionary says counselor or teacher, and Gandalf certainly gave counsel.
Oh, never mind on the first part then.
On to the second, I leave it up to the Op then as I don’t think he meant a character like Gandalf.
To this end, I think Obi-Wan Kenobi and Yoda could easily qualify as the Svengali-type. “What I told you was true…from a certain point of view. And now, before we (essentially arbitrarily) decide that you get your official Jedi Decoder Ring, we’re going to need you to go ahead and kill Darth Vader, thereby rectifying what we effed up 20 years ago, before you were even born, mmmkay?”
Merlin was mentor to Arthur.
Batman, mentor to Robin.
You misspelled “emotionally abusive fuckwit intent on passing on his own psychoses to teh next generation rather than getting himself the therapy, drugs, & electroshock he so obviously and desperately needs.”
Socrates Fortlow in Always Outnumbered.
So, you’re an All-Star Batman reader, then?
I can’t believe someone beat me to the Shazam! reference
Dammit! I was just coming in to say Bill Batson’s Mentor. Does it get any Mentor-er than that?
Hell, primary-continuity Batman is only incrementally better.