The Sage is the "old wise one" that is often refered to in stories. Well, they don't necessarily have to be old, just wise. The Sage can be thought of as a teacher and student. They spend their time gathering knowledge about the universe, and sharing that with others. In fact, the Sage has the ability to improve other party member skills!

They also have a Mythology skill that helps them identify various attributes about people or lifeforms they meet.

Sages have a skill called Linguistics that can help them speak with various lifeforms that aren't of the same culture, or read languages that others may not be able to understand.

Even though Sages aren't spellcasters, they do have the ability to invoke magic staves!

Sages do have a curiosity for magical writing, and can sometimes utilize lesser powerful magical scroll and books (like Scribes).

Because of their vast knowledge, Sages have the ability to identify a lot of unfamiliar items, and obtain information about their properties (Item Lore skill).

As if this isn't enough, they can also provide general information to help the party throughout their adventure (Intuition skill). For example, they can know the percent change of a spell being successfully cast by another party member at a given power level. You'll never know all the ways the Sage vocation will benefit the party!