Kirev Firiskiy was a Great Knight orphan born in the capital of Invinojug who was moulded into one of the elite Juggernauts, trained from childhood to be the diehard troops of the Great Knights. He was a good friend of Pepin, having known each other since childhood. Unfortunately for both of them, Kirev was sent on an expedition westwards, where they ventured into the Maxilla Peninsula (where Medusa's Castle is located). When he returned, he was incredibly different, now incredibly loyal to the Great Knights, and much more brutal. Unbeknownst to Pepin, the real Kirev was actually dead, and was instead possessed by Lord Verick. His new attitude drove the two apart, and when Kirev arrived to replace Pepin as the leader of the Eclipse Expedition, Pepin was extremely bitter about this. Kirev commanded many of the Great Knights to their death, claiming it was for the good of the Great Knights. This finally caused an insurrection against Kirev led by Pepin and Vince, which was barely suppressed and lead to the loss of Kirev's form. Verick abandoned the body for his new form and later killed Pepin, leaving Kirev's dead body in the wilderness of Rovaltinny.
Kirev was born in the Great Knight capital of Invinojug. He rapidly became an orphan when his mother died in childbirth, and his father died soon after from a plague which swept Invinojug only a month after Kirev's birth. Consequently, he would never know his parents, and was sent to an orphanage to be raised.
As he grew older, it was clear that Kirev wanted to be a warrior, often dominating his friends in play-fighting and performing exceptionally well in a number of physical fields, claiming that he was training to be "the best soldier ever". This eagerness to be the best was noticed by General Agisiem, the leader of the experimental "Juggernaut" programme. This military programme was designed to create a new breed of soldier with unwavering loyalty to the Great Knights by using experimental training techniques from the age of 7 onwards. Kirev was taken away to a camp in the Eagle Mountains, where he was trained mercilessly.