J'nanin, whose name is based on the Sanskrit word for "knowledge", was written by Atrus as a hub Age for teaching his sons about the Art. It later became a prison for Saavedro, a Narayani native who was marooned on the Age after Sirrus and Achenar had plundered his home.
Like many of Atrus's Ages, J'nanin is a small island in a seemingly endless ocean. The island itself is a bowl-shaped mass, with the center depression resting below sea level. A small lake fills the base of the depression, though the rest of the island is barren rock. Four massive, hollow tusks jut up from the terrain - three around the perimeter, and one in the center. The three tusks around the rim of the island have rooms rooms built into them which serve as the linking chambers for the lesson Ages of Amateria, Edanna, and Voltaic. Equipment for unlocking the doors to these chambers dots the landscape.
A circular observation deck rests atop the central tusk, with telescopes that look out at the lesson Age tusks. Properly calibrating these telescopes provides the key to accessing the Linking Book within. An opening in the center of the observation deck's floor contains a cage holding the Narayan Linking Book. This Book is progressively unlocked by entering special Narayani mantra patterns into an adjacent scanning device. An elevator connects the observation deck to a chamber at the base of the central tusk that Saavedro used as his living quarters and lab during his exile. Outside is a small greenhouse that opens onto the lake.
This Age was originally conceived as a hub world, where Atrus could teach his sons how to write Ages of their own. His lessons were delivered to them through an imager in the central tusk's observation deck, rather than in person. Each of his four lessons had an Age associated with it, and a thematically-appropriate puzzle needed to be solved in order to access each one. Once the boys had completed the three Ages linked from the tusks around the perimeter of the island, the link to Narayan — the final lesson Age — was unlocked.
Several years after finishing their lessons, Sirrus and Achenar returned to J'nanin and used it as a base of operations while they exploited and nearly destroyed the Narayani by promising to "fix" the Age and free its people from the requirements of their traditions. When Saavedro followed them back to J'nanin to plead for them to fulfill their promises, they tied him to one of the reflector posts and linked back to Myst, burning the Linking Book in front of him as they left. For twenty years, Saavedro was left alone on J'nanin, lost in madness and unable to return home.
In 9468 DE (roughly 1817 CE), Atrus returned to J'nanin while struggling with the task of writing Releeshahn for the D'ni who had survived the destruction of their empire. He left without seeing Saavedro, but left behind a Linking Book back to his new home in Tomahna. Saavedro followed him and learned about Atrus "restoring" the D'ni people. Mistaking Atrus's restoration plans with true resurrection, Saavedro saw an opportunity to coerce Atrus into repairing the damage his sons had wrought to Narayan. He recorded new messages into the imagers, and modified many of the machines and puzzles in J'nanin and the other lesson Ages, intent on forcing Atrus to relive his past mistakes. When he was done, he returned to Tomahna to steal the Releesahn Book, meaning for Atrus to follow him. By chance, however, the Stranger was visiting Tomahna at the time. Caught off guard, Saavedro tried to distract both of them by throwing a firemarble, which set Atrus's study ablaze. In the ensuing conflagration, the Stranger was the only one able to follow Saavedro before the fire consumed the J'nanin Book.
After successfully retrieving Releeshahn and reuniting Saavedro with his people, the Stranger returned to Tomahna. J'nanin has been abandoned ever since that time.