Yeesha is the daughter of Atrus and Catherine, sister of Sirrus and Achenar. She first appeared in Myst III: Exile, and has also appeared in Myst IV: Revelation, Myst V: End of Ages, and Uru taking more dominant roles in the storylines of each game.
Yeesha is the youngest daughter of Atrus and Catherine. She was born after the events in the Book of D'ni and after the Riven game. She first appears as a baby in Catherine's arms at the beginning of Exile. Her brothers Sirrus and Achenar have already found and been trapped in Spire and Haven respectively so for the first several years of her life she grew up as an only child.
During her childhood, she spent her time working with her parents, making puzzles, playing by the water, and playing with the "Fun Club". Atrus gave her a journal as a gift so that she adopted the custom of journal-keeping. Her bedroom had a bookshelf with a mechanical combination with the names of her family, which was replaced with D'ni, as she knew ore about D'ni language. After Atrus put linking chambers in Haven and Spire to allow the family to visit the brothers she gets to meet them. Achenar wanted to make her a gift of bones, but Atrus made her go before she could see it, making him sad when they left.
Like her brothers before her, Yeesha was taken to Serenia and befriended Anya, one of the Protectors. As Sirrus told her, she saw all the memory globes hanging from the ceiling of the Memory Chamber. She was excited about Serenia and wanted to visit it again. Despite her father's scientific explanations, during their other stays there, she started being interested in their customs and traditions, and saw a water spirit guide, but her father explained it would be a fish. She also became excited with the idea of training.
She expressed to her father that she would like to visit the Dream Realm. Although Atrus explained that Dream can't exist, she insisted that she wanted to investigate it herself. After 3 months, she was honored in a ceremony celebrating the completion of her training, and her parents attended it. She received a Protector's necklace marking her mastery of the Serenian customs.
For the following days, she surprised her parents by displaying an uncanny knowledge about things she never witnessed. Yeesha was never told about the circumstances of Anna's death, but one day while she held her picture, the necklace "talked" to her, and she realized that her mother doesn't write Ages any more as she has regrets that Anna died in one of her Ages. During one of the writing lessons with Atrus, she expressed her sadness and proposed to Atrus to explain that she shouldn't consider her responsible. Atrus was surprised, knowing that Yeesha was never told about it, and he was even more puzzled when Yeesha mentioned the necklace.
Catherine believed that the siblings came to adore each other, and through Yeesha there would be hope for their family. Nonetheless the matter caused tension between her and Atrus, and although they took care not to disagree in front of Yeesha, one day she surprised Catherine asking if they still argued.
Sirrus uses her to escape from Spire. She runs to Haven for protection and Sirrus destroys the cage in Haven as well to get to her. He captures her and then takes her to Serenia where he intends to use the memory chamber of Serenia to put himself in Yeesha's body, learn the art of writing and then kill his parents. This starts the events in Myst IV: Revelation.
By the end of this both her brothers are dead.
When she gets older she sets off to 'find herself'. Like Gehn, she goes to the uninhabited D'ni and she also goes to Anna's desert cleft. During this time she meets an old D'ni writer named Calam who has returned. He adds to her knowledge of the art and becomes a moderating factor in her style of writing. During this time she learns of ancient D'ni prophesies about the grower, which she believes is Calam. She and Calam also learn about the Bahro who have been trapped in servitude to the D'ni through control of a sacred tablet of theirs. However, Calam gets murdered.
In a fit of rage she destroys Calam's murderer. However, she also learns through this the power that she has and comes to believe that she might be the grower. With the help of the Bahro she learns to do things with her writing no D'ni has ever been able to do such as Relto. Eventually she went on a quest to free the Bahro by gaining access to their sacred tablet. Being so full of herself she fails and learns humility in the process.
After this people first start to gather to the D'ni cavern from the surface (Uru) and the way becomes clear to her how to get a second chance to free the Bahro - through another individual. This brings about the events in Myst V: End of Ages. At the end of this the Bahro are free, the D'ni have rebuilt their society in Releeshahn, The D'ni cavern is beginning to flourish with new life (from the surface) and her burden is over. She can join her father Atrus (now an old man) in Releeshahn.