So you want to be a hero? Fight bad guys, right wrongs, defend the innocent; that kind of thing. Do you think that heroes just pop up out of nowhere? Of course not. From superhero to chosen one, martial arts expert to super spy, heroes spend years (or at least an epic montage) training to become what the world needs them to be. And while there are a few self-taught capes flying around, most every other kind of hero needs a mentor. Someone who can teach them the skills that let them survive the fights and adventures that would fell us mere mortals. But sometimes that mentor can break bad, forcing the hero to face down his former teacher in a trope I like to call The Mentor Gone Bad.
To be clear this trope does not apply to mentors who were either openly or secretly evil in the first place. Just because the hero finally realizes that their teacher is a bad hombre doesn’t mean the mentor went bad. It just means the hero was too naïve to realize what they were getting themselves into. Nor does the realization that the person you look up to is flawed qualify either. Far from perfect is still far from evil. No, to truly fit this trope the mentor must have genuinely been a ‘good guy’ and then because of disillusionment or tragedy gone over to the dark side.
In my mind, the best example of this trope is found in season two of Arrow, where Slade Wilson goes from the man who is keeping Oliver alive for a whole season to the man actively trying to murder him. A combination of jealousy, rage, and a mind-altering drug cause Slade to have a psychotic break; turning him into the villain Deathstroke. Another great example (well two actually) can be found on the show Chuck. In two different episodes, former mentors of Casey’s come back after having become disillusioned with government work and deciding to work for their own benefit. Both are among the best episodes in the shows run but in terms of this trope neither truly hold a candle to the season-long rise and fall of Daniel Shaw, American Hero. In season three Shaw is brought in to turn Chuck into a real spy, he becomes a role model and a mentor to Chuck. But when he learns who actually killed his wife he turns on the team and becomes the closest thing we see to an evil version of Chuck in the whole series. While the season might have been a bit uneven, its fair to say that Shaw might have been the show’s best villain.
This trope isn’t limited to television. The first Mission: Impossible movie used it to great effect using Jim Phelps’ betrayal of Ethan Hunt as the impetus for an entire franchise of Tom Cruise action movies. Of course, taking a beloved character and turning him into an amoral murderer certainly didn’t play well with fans of the original tv show (or for that matter the show’s cast), but it was an effective twist in an era before big twists were a thing in blockbusters.
The title of most famous mentor gone bad though may belong to a character whose betrayal is featured in both an all-time classic book series and in an Oscar-winning trilogy of films. In Lord of the Rings Saruman the White is the head of Gandalf’s order and considered the wisest and most powerful of wizards, but he is corrupted by Sauron and turns on Gandalf and the cause of good. In the end, he becomes as large a threat as Sauron and in some ways a much more personal one.
Which is why The Mentor Gone Bad is such an effective and commonly used trope. It gives the audience a villain that both it and the protagonist are emotionally invested in. A foe who knows the hero’s strengths and weaknesses intimately. Their fall from grace gives the characters a note of tragedy and sympathy and a sense of there but for the grace of God go I. They also allow the hero to prove they have outgrown their teacher by defeating them and their plans. As far as storytelling tropes go this is one of the most useful and powerful ones out there if it’s used correctly. If you plan on using it maybe you should find a mentor to teach you how to do so effectively. Just make sure none of their loved ones work in a highly dangerous field.