Every hero needs to learn a lesson and by learning that lesson, he (or she) can defeat the villain. To learn this lesson, you rhero needs a mentor.
The difference between your hero and your villain is that your hero learns to change while your villain does not, and this inability to change causes the villain’s downfall.
To help your hero learn and change, your hero needs a mentor. The mentor has his or her own goal and meets the hero through the indirect actions of the villain.
In “Star Wars,” Darth Vader’s trying to find the smuggled Death Star plans that Princess Leia has hidden in R2D2. When R2D2 runs off to look for Obi-wan, that causes Luke to follow and run into Obi-wan as well.
In “Rocky,” Rocky’s coach is his mentor who teaches him how to box against Apollo Creed. Rocky already knew this coach before, but the two now work together because Apollo Creed picked Rocky to fight against.
In “Ratatouille,” Remy the rat’s mentor is the chef spirit from the cookbook, who appears before him.
The hero’s relationship with the mentor forms a sub-plot because the mentor is also pursuing a goal. Like all sub-plots, the hero/mentor relationship gets started after the story begins, but may be resolved before the hero achieves his goal or afterwards.
In “Die Hard,” Bruce Willis’s mentor is the black police officer who shot a kid by mistake. This police officer helps motivate Bruce Willis near the end of Act II when he’s trapped in the bathroom, pulling glass shards out of his feet. Bruce Willis achieves his goal first by killing the head terrorist and rescuing his wife, then the black police officer achieves his goal by regaining the courage to use his gun by gunning down the last terrorist.
In “Rocky,” the coach achieves his goal before Rocky when he trains Rocky to the best of his ability. He’s had a chance to train a fighter for the championship. Now it’s up to Rocky to achieve his goal of standing on his feet for the entire fight.
Your mentor has a goal that may not be identical, but is similar to the hero’s goal. The hero and the mentor need each other to succeed. The mentor’s quest for a goal is a mini-story with its own exposition, rising action, apparent defeat, and finally achievement or loss of the desired goal.
Your hero must begin with a flaw and the mentor must help the hero learn to overcome that flaw. Then during battle with the villain, the hero needs to use that knowledge to defeat the villain.
Make sure your hero has a flaw and make sure your hero meets a mentor to help him overcome that flaw. Perfect heroes are boring because they do not change, and we don’t expect someone to change by themselves without outside influences, and that’s the role of your mentor.