Glen was born and raised in southern Grado farmland. As children, Glen and his brother had to chase animals from their fields by throwing sticks and stones at them. This skill came into use one day, when the Emperor's procession decided to pass through Glen's village. Watching the Emperor from the top of the tree, the two boys spotted a dog harrying the procession and drove away the dog by throwing objects at it. Unfortunately, some of the Emperor's guardsmen were also hit by the projectiles and the soldiers decided to arrest the boys. Emperor Vigarde personally chastised the soldiers who arrest Glen, and invited him and his brother to a feast. This feast culminates with the brothers enlisting in the Grado military, and Glen's eventual rise in both rank and fame.
Near the beginning of the game, Glen is given the task of finding Princess Eirika, and thereafter to eliminate her and obtain her bracelet. Glen reveals to his brother that when Renais and Grado were still close, he had met the Princess once before and found her to be a kind and gentle person. It is this meeting that causes Glen to doubt his Emperor's words that Eirika had killed the citizens in the country of Carcino. The two eventually meet again as Eirika's convoy is passing through Caer Pelyn to enter Jehanna. As they converse, Eirika disproves Vigarde's accusations against her. This leads Glen to frustrate over the reason why the Emperor would lie to him, and he lets Eirika go, resolving to postpone their battle until after he talks with the Emperor again.
As Eirika leaves, Glen is confronted by General Valter, who reveals that his exile by the Emperor and his hatred for Glen's plea for peace drives him to kill. The two are drawn into a duel, and Glen is murdered. It is Glen's murder which serves as the catalyst for Cormag's eventual defection from the Grado army in Eirika's route.
In somewhat of an oddity, Glen's death at Valter's hands is not mentioned at all in the English version of Ephraim's route. Although a spy in a house in Chapter 15 mentions Glen died in the mountains of Carcino, Valter is not explicitly pegged as the culprit unless the player takes Eirika's route. In the Japanese version of Ephraim's route, Glen's death is offhandedly mentioned in Valter and Cormag's battle conversation; instead of saying "Let's see if your lance is as sharp as your tongue," like he does in the English version, Valter says "Let's see if you're more entertaining than your older brother!"
Unlike most of the non-playable Grado characters, Glen is an anti-villain, like Selena; unlike Selena, who was completely loyal to the Emperor even after finding out the truth behind the situation, Glen is open about his doubts and doesn't trust the "new" Vigarde at all. Also unlike Selena, who is known for her honor, Glen is willing to do arguably less honorable acts such as granting permission for Saar to kill Natasha if she resists arrest (likely knowing that Natasha, a Cleric, cannot fight back) and pretending to believe Vigarde's lies about Eirika in order to test her.
In contrast to General Valter, Glen is a compassionate young man, whose honor, integrity, and love for his Emperor ultimately serve as his undoing. Through the course of the game, Glen, along with his younger brother Cormag, become increasingly suspicious of Emperor Vigarde's activities.
*40% in the Japanese version
**25% in the Japanese version
Subjective: The following part of this article is subjective to the editor's writing. Therefore, it may not work for everyone.
Glen is a solid unit despite having only a few levels of growth. His strength and defense are nearly as good as Cormag's, and when equipped with a Killing Edge or Killer Lance (or both) he can defeat almost anything in one hit. He is not at the level of Ismaire in terms of unaided skill, but he definitely comes in handy against things like Cyclops or Baels.