I promise not to go through all the different characters in the hero’s journey, but I have to mention the mentor. The stereotype of the mentor is the wise old man or wise old woman, or it is a good witch as in the Wizard of Oz. The mentor usually gives the hero a special gift that will help him or her along the way, like Dorothy got the ruby slippers.
Of course a person can be their own mentor. Watch for mentors in books and movies. Be creative with your own mentors. Give your readers something different. You can combine the different roles, like a threshold guardian who turns out to be a mentor. I had wise mentor in my first novel who died in the first chapter. But his memory lived on, while a foul-mouthed doctor became another sort of mentor.