Prior to the Great Cataclysm, Jaa inhabited Ko-Metru. He worked as a Scholar and, at some point, aided Toa Nuju in his search for Ehrye. Jaa stayed in Ko-Metru until the island's Matoran population was taken away by the Vahki, who were being commanded by Makuta Teridax in the form of Turaga Dume. He was put into a Matoran Sphere.
Later, when the Toa Metru rescued all of the Matoran, he was reawakened on the shores of Naho Bay.
Due to the fact that Jaa was in a Matoran Sphere his size and strength was decreased. He also lost all of his memories. In the first years of The Dark Time he worked with all of the other Ko-Matoran on creating the village of Ko-Koro. The village leader would be Turaga Nuju former Toa Metru of Ice. They made the village out of dismantled Airships.
Later in Jaa's life he became a Scribe in Ko-Koro. After the Bohrok-Kal were defeated Jaa and the other Matoran were rebuilt into larger, stronger forms like they had been before the effects of the Matoran Spheres.
Return to Metru Nui
Jaa helped to construct the boats to return to Metru Nui, and also heard the Turaga tales about Mata Nui.
Jaa and the other Matoran of Metru Nui celebrated Mata Nui's awakening in the coliseum when they heard Teridax proclaiming to have become the Great Spirit, and that now he ruled the Universe. The Matoran then scattered then separated to avoid being captured by Teridax. It is unknown what Jaa did until Teridax landed on Bara Magna
During Teridax's fight with Mata Nui on Bara Magna, the blows that Teridax recieved created various earthquakes, and these caused the majority of the Matoran Universe population to be evacuated in shleters. Thanks to this, after Teridax's head collided with Aqua Magna, Jaa and many other Matoran and other beings were able to survive. As Teridax was killed by the impact, the Matoran Universe had three days before it ceased functioning, turning it into a world with no light, heat or air, and Jaa had to join the mass exodus to escape to the reformed Spherus Magna. He is currently residing there.
- Mata Nui Online Game II: The Final Chronicle