Pilot Name: Guilliam Yeager
Voice Actor: Hideyuki Tanaka
Group: Divine Crusaders (Earth Federation)
Nickname: None
Theme Song: Time to Come
Units Piloted: Gespenst R, Gespenst MK-II R, XN Geist
Games Appeared: 4, F, F Final, Original Generation, Original Generation 2, and Original Generations.

It's assumed that after Guilliam was defeated by the Alpha Force, he ended up joining the AEUG in another world due to his amnesia. He eventually regained his previous memories. He continued to travel to other dimensions in order to atone for his past mistakes, and appeared in several different timelines.

He later ended up at the homeworld of the Shadow Mirror. Guilliam researched System XN at Tesla Leicht Institute, a device that is capable of traveling between two dimensions using two parts, Agyieus and Lykeios. He did this in hope of one day returning to his home world. He failed during the activation of Agyieus, and was then sent to yet another new world. System XN was left behind, and the Shadow Mirror forces obtained it. It took two years after the Shadow Mirror occupied Tesla Leicht Institute for them to dimension jump to the world that Guilliam went to.

In the new world, he's 27 years old, and his ranking is a Major. He's a former member of the elite group known as the Aggressors. He helped the Hiryuu Kai while it was in space during the DC war, but disappeared shortly after. He reappeared later in order to help the Hagane and Hiryuu Kai's forces take out the Aerogators.

During his battle with Ingram, he reveals that he comes from another dimension, wandering, looking for a certain group of people. He tells Ingram that defeating him and the Aerogators are his top priority right now.

Later, Galuin attacked the Hiryuu Kai and Hagane. Guilliam suspected him of being Commander Kar-Wai from the old DC guard unit. After the battle, Guilliam was sure that he knew the Aerogators motives. After Kar-Wai Lau's death, Guilliam swore that he would get revenge against the Aerogators for what they did to his old Commander.

Later, after the Shadow Mirror traveled to this world, it's revealed that they had their eye on him because of his ability to travel across dimensions using System XN.

Guilliam knew that Vindel had obtained Agyieus, but wondered what happened to Lykeios, and decided to ask Lamia about it. It's large, therefore it remained in the Shadow Mirror's homeworld. Lamia confirmed its destruction, and explained that they did it so none of their enemies would be able to follow them to this world.

Guilliam noticed that some mysterious people had arrived, and went out with Lamia in order to investigate. They encountered Raul's group, and helped them fight against Axel's squad, forcing them to retreat. Guilliam offered them an explanation as to where they ended up, and even gave them the chance of joining the Hiryuu Kai and Hagane's forces, while keeping their origins a secret.

Guilliam had it completely destroyed after the heroes escaped from the Einst space area, because he feared that it would be misused once again. Guilliam lost his only way to return back to his former world with its destruction.

Guilliam various expressions