Very little is known about Agath's past. He was the brother of the Jaredite sorcerer Akish, who conspired against his own people in his quest for power. At some point in the past, Agath was appointed by Akish to be a commander in his army.
Agath is sent by Akish to lay siege to the Jaredites' encampment in the wilderness. The Jaredites, led by King Omer and Asherah, are forewarned of the attack by the Liahona that Joshua Plimpton and Marcos have in their possession. The Jaredites evacuate the area, but Agath continues to follow them.
Joshua and Hamira are scouting around when they find Agath, along with his warriors and cureloms, still searching for the Jaredites. Joshua and Hamira ambush Agath's army and cause a massive commotion. Most of Agath's army falls off a nearby cliff, but Agath confronts Joshua and Hamira. The two of them climb into the rider's basket atop his curelom and set it on fire. Hamira uses her dagger to kill Agath before his curelom falls off the cliff.