General terms:
* Mentor: This is a common term for a wise and trusted advisor who guides and teaches a protagonist.
* Counselor: This term implies someone who offers advice and guidance, often in a more formal setting.
* Guide: This term suggests someone who helps a protagonist navigate a specific situation or journey.
* Sage: This term implies someone with great wisdom and knowledge, often older and respected.
* Oracle: This term suggests someone who provides prophetic or enigmatic advice.
Specific titles:
* Teacher: This term is used when the advisor is formally instructing a protagonist.
* Master: This term implies a more authoritative and possibly more experienced relationship between advisor and protagonist.
* Friend: Sometimes, the advisor is simply a close friend who provides guidance and support.
* Guardian: This term implies someone who protects and guides a protagonist, often physically.
* Prophet: This term is used when the advisor has visions or receives divine messages.
Ultimately, the best way to describe an advisor in literature is to consider their role in the story, their relationship with the protagonist, and the nature of their advice.