Who is Mason Ashford from Frostbite and what is their importance?

Mason Ashford is a boy who attends the academy with Rose and Lissa. Mason has had a crush on Rose for a long time. After Rose learns that Dimitri is more than likely going to become Tasha's guardian, Rose begins seeing Mason. They become intimate once, but Rose cannot stop thinking of Dimitri and ends the moment. Rose decides to break up with Mason, but then learns that Mason has gone to kill the Strigoi they think are living in Spokane. Rose is forced to go after Mason and save him. Unfortunately, Mason's concern for Rose causes him to place himself in danger and he is killed.