Mason Ashford is a dhampir who is one of Rose Hathaway's best friends, and an also a novice guardian like her. He helps Rose out a lot throughout the series. He is interested in her romantically, and Rose eventually attempts a relationship with him, only to find it falling apart because of her unbreakable connection to Dimitri Belikov. Mason's life is ended in Frostbite after trying to save Rose. After making it into sunlight, he returns into the shade of the building while attempting to kill the Strigoi. He dies when the Strigoi who goes by the name Isaiah snaps his neck, much to Rose's devastation.
In Shadow Kiss, Rose sees his ghost around the Academy as the result of the weakening wards. Mason tries to give Rose clues but is waved off, she thinks she's going crazy. Later on, he appears to her and manages to tell her, "They're...coming..." meaning Strigoi were on campus. After the wards went back up he was locked out so Rose went off campus to get him to show her where the Strigoi were hiding. When asked by Rose he points out on a map where the Strigoi are hiding while the sun is up.
After the rescue mission in the Strigoi infested caves, Rose is desperately trying to find Dimitri. She isn't sure if he's dead or alive. She consults Mason about it, asking him questions about Dimitri. When asked if he was dead or if he was alive, Mason immediately shakes his head. When Rose asks if Dimitri became a Strigoi, Mason is hesitant to reply it but eventually nods, revealing that Dimitri has been changed.
At the end of Shadow Kiss, Mason's forty days as a ghost because of his young, violent death has come to an end. He is described as faded out when making his last interaction with Rose. He finds peace and finally leaves.
Mason is described as being handsome with red hair that sticks up in every direction, blue eyes (appear brown in the graphic novel) and freckles.He is seen as being muscular and tall figure, according to Rose the body type of a fully trained Guardian. Mason is seen as being very attactive to girls as Rose and Mia both agreed that Mason was cute and handsome.
Mason was seen as being a brave, selfless and understanding person. He also as being extremely funny and sharing a sense of humour similar to that of Rose and Christian. Though despite this Mason was prone to jealously espsically when Rose was concerned due to his feelings towards her, but he also felt that he needed to prove himself to others.
He was also seen as selfless when he attempted to save Rose from Isiah in Spokane which unfortunatly lead to his death. Even in death, Mason was seen as helpful towards Rose in warning her about the upcoming Strigoi attack but also that he didn't hold any ill feelings towards Rose because of his death, as when he moved on he was seen laughing sweetly.
Mason was simply and plainly in love with Rosemarie Hathaway. They were very good friends.They had many classes together, but also connected because of their love for pranks and humour. Mason was willing to do anything for Rose, as she convinced him to get her St. Vladimir's diaries from Christian Ozera in the attic of the church. He was also protective of Rose especially when other males would insult her.
In Frostbite, they began dating. When Rose kissed Mason he looked as though his birthday wish had come true, but he was prone to jealously against Adrian Ivashkov and others. In Spokane, Mason was going to protect Rose from Strigoi when she was cornered in the living room. Mason went out of the sunlight to save Rose, but he was killed by Isaiah almost instantly. Rose, in grief, killed both Isaiah and Elena in the living room and stayed with Mason's body, refusing to leave.
In Shadow Kiss, Mason was seen several times by Rose, due to her shadow-kissed status, where Mason continued to protect and be of help to Rose. When Mason moved on it was shown that he never blamed Rose for his death, and that he hoped she would be happy in the future.
Eddie Castile was Mason's best friend. Their relationship was similar to that of brothers as they both supported and joked together. They both had similar personality to wanting to protect the Moroi; this eventually lead to them going to Spokane to find Strigoi. After Mason's death, it was seen that this greatly impacted on Eddie changing his personality and emotionally stability, though it was seen that Mason cared deeply for Eddie, as he saw him as his brother. In Bloodlines, Eddie falls for Jill dragomir but meets a human called Micah that has the same personality and looks as Mason. Micah has a crush on Jill as well and feels as though he owes it to Micah because he still carried guilt over Mason's death.
Mason was seen have respected and look up to Dimitri Belikov, he was one that famously called Dimitri a "God" to Rose. It could seem that Mason was inspired by Dimitri.