|“||I know something's going on. I know you don't want to talk about it. But you're still my best friend. And, um, considering the fact that the last good friend I made turned out to be a professional killer, I don't have too many options for new ones. So, when you're ready to talk, talk. Until then, I know I can kick your ass in at least one of these games.||”|
— Mason to Liam in A Promise to the Dead
Liam and Mason have presumably been best friends since they were children, and their friendship has seemingly never wavered since that point. In early 2012, after Liam was inadvertently given the Bite by Scott McCall and turned into a Beta werewolf, Mason immediately knew that something was going on with his best friend, but understood that Liam needed to tell him in his own time and did not push him to reveal his secret.
In the beginning of Season 5, Liam was finally forced to reveal his werewolf nature to Mason after they were chased by a brown wolf in the high school, but rather than being afraid or angry, Mason was instantly accepting of this revelation and wasted no time in joining the McCall Pack to help them fight supernatural threats. However, it was soon revealed that Mason, who was a genetic chimera due to having absorbed his own twin in the womb, had become the Dread Doctors' sole successful Chimera, which led him to become the host for the spirit of the Beast of Gevaudan, Sebastien Valet, who had previously been killed in the 18th century. As the host for Sebastien's spirit, Mason gained all of the powers of the Beast and was unconsciously forced to transform by the Doctors using frequencies, causing him to slaughter several dozen people over the course of several weeks. Upon learning that Mason was the Beast, Liam and the rest of the McCall Pack dedicated themselves to saving Mason's life while also defeating the Beast, a feat that they were eventually able to fulfill against all odds, allowing Liam and Mason to reunite once again.
Liam and Mason are also known as Liason by fans.
In The Benefactor,
In Required Reading,
In The Last Chimera,
In Lie Ability,
In Maid of Gévaudan,