Archetypes

Four archetypes support a thesis.

thesis 1  -  thesis 2
mentor   - nemesis (dark mentor)
attractor - dark attractor
sidekick - dark sidekick

two embody theme
protagonist - trickster

A mentor will train you to use the thesis they support.  They will give you tools, or take tools away, whatever is needed to apply their thesis towards the theme(goal).

An attractor will argue for the validity of the thesis they support.

A sidekick will help you when you support the thesis they support.

Note:
The protagonist is not the same as a nemesis.  How many times have you heard the dialog from the bad guy, "You and I, we're the same."  "We're not that much different."

The reason this resonates is because both the protag and the nemisis(dark mentor) want to use the same elixer, the same reward, the same emotion, the same tool, the same weapon in order to reach the goal.

In star wars it's "the force."  In Batman Begins it's "Fear."  In Shawshank Redemption it's "Hope."  In Schindler's List it's "Gratitude." In Pulp Fiction it's "Second Chances."

It's what the mentor characters use and what the protag and trickster want to know how to use.

The other reason the protag and nemesis are close is because each thesis is one said of the same coin.  So the protag is just as close to the mentor as the nemesis.

The Trickster archetype is the Twin of the protagonist.
Agent Starling and Dr. Chilton
Luke Skywalker and Han Solo
Oskar Schindler and Amon Goeth
Red and Andy Dufresne