Galen is the illegitimate half-brother of Regal Farseer through Queen Desire, although this is not public knowledge. Galen was brought to Buckkeep from Farrow as a child and was apprenticed to Skillmaster Solicity. He became Skillmaster after Solicity's death, despite his incomplete training, unremarkable talent, and limited knowledge of the Skill's history and usage.
Galen became responsible for teaching the Princes Chivalry and Verity the Skill. During one lesson, Chivalry inadvertently Skill-commanded Galen to be loyal to him. The totality of the command is such that Galen could thereafter only feel blind worship for Chivalry. Galen is even incapable of blaming Chivalry for his own death; instead, he directs his anger toward Fitz, for whom he harbors extreme prejudice.
Galen is petty and rude to those he feels are beneath his station, including the Fool; he is disliked by most Buckkeep Castle servants. He believes that the Skill is only learned through absolute control, a belief which gives rise to his sadistic teaching methods.
Galen is instructed to form a Skill coterie by King Shrewd due to the increasing threat of the Red Ship Raiders. After Patience badgers Shrewd to educate Fitz as befits a prince, Shrewd decides to allow Fitz to join Galen's lessons. Galen refuses to teach Fitz, but Shrewd overrules him.
At the first lesson, Galen's teaching methods are revealed to be extremely strict. His lessons begin before sunrise, with the last to arrive receiving physical punishment, and students are not released until after sundown, with no food or water in between. He insists that his students dine together and keep a bland diet. After Fitz sneaks some meat from the kitchens for Smithy, Galen shames him in front of the other students for eating forbidden food and beats him.
Galen's teaching methods soon drive several students to quit his lessons. His dislike for Serene is obvious, as is his favoring of August. Galen's severe dislike for Fitz also quickly becomes clear to Fitz and the other students. Galen is enraged by Fitz's quick progression and confidence with the Skill and Fitz's ability to guard his personal thoughts against Galen's probing.
The first time Galen and Fitz attempt to reach each other simultaneously with the Skill and touch minds unguarded, Galen imprints a Skill-command on Fitz to die. Fitz instantly becomes desolate and inconsolable, and Galen, satisfied, leaves him in the Queen's Garden. Fitz subsequently attempts to kill himself by throwing himself from the tower, but he is stopped by Smithy and later found by Burrich and the Fool.
In response, Burrich forcibly brings Galen to the Witness Stones and demands hand-to-hand combat. Burrich thoroughly beats Galen. Galen is unable to hold his lessons for several days.
When Galen finally returns to the Queen's Garden, he is surprised to see Fitz has also returned. Galen no longer singles Fitz out for punishment, instead directing his efforts towards the other seven members of the class. They begin to form a coterie that soundly excludes Fitz's feeble efforts.
Shortly before Springfest, Galen announces that the students will face a final test to determine their abilities and bond as a coterie. He tells his students that they will each be taken separately to a different location, where they will receive Skilled instructions on how to return to the castle. Before Fitz departs, Galen accuses him of being Burrich's catamite and drawing on him for strength, threatening Fitz that he will not allow it to continue; Fitz believes Galen is referencing the Wit-bond Fitz has with Smithy.
Galen has Fitz deposited north of Forge and left to make his way back on foot. The other students are supplied with horses, and all but one return by the start of Springfest. Galen presents them as his coterie. When Fitz encounters Galen some weeks after returning to Buckkeep, Galen's comments imply that he had intended Fitz to be killed by Forged Ones during his test.
Galen remains at Buckkeep for Verity's wedding to Kettricken. After Rurisk is poisoned and Cob killed, Regal complains to Galen that the situation has gotten out of control. Galen reassures Regal that the next day's wedding will go off without a hitch, and that while he cannot sap Verity's strength without touching him, once the touch occurs Verity will fall to him with ease.
Galen readies himself for the wedding and positions himself beside Verity, ostensibly to act as King's Man for him. He reaches for Verity and begins stealing his strength instead. However, Fitz, having overheard the previous evening's conversation, manages to warn Verity of Galen's treachery. Verity uses Fitz's strength to overpower Galen with the Skill and kill him.