Benjamin Cole is a human merchant. As an NPC, Benjamin Cole is played by Matthew Mercer.
Benjamin is quite wry, and no nonsense. He seems to take his job, and the hobby of book collecting, very seriously. According to Vex'ahlia, he revels in his strange power he has over his customers.
Benjamin is the keeper of a bookstore in Vasselheim. He has, on multiple occasions, charged Vex'ahlia (and presumably others) far too much for old books.
"The Sunken Tomb" (1x44) Edit
While looking for information on the Raven Queen, Vex'ahlia met Benjamin while attempting to read a book without buying it. He insisted that she purchase the book if she were to read it, and upon realizing that she had no intention of doing so, took the book from her and declared that there would be no sale. Vex caved and paid full price, giving Benjamin the honor of being the first person to ever make Vex pay full price.
"As far as you're concerned right now, my name is no sale." (Benjamin shutting down Vex's haggling attempt)