Ti'ana, or Anna (human name), is the wife of Aitrus, mother of Gehn and grandmother of Atrus in the Myst series. She was introduced in The Book of Ti'ana and her story is continued in The Book of Atrus, though she dies at some point before the events of Myst (her grave can be found in realMyst).
Book of Ti'ana
Her father used to say to her about The Whole image of things; how looking at a problem from any angles, considering how the pieces are interrelated and coming up with answers.
As a young girl, she assisted in the study of the volcano which stood atop the Great Shaft that led down to D'ni. After the death of her father, she decided to explore the cavern in the volcano one last time and accidentally stumbles into D'ni, where she is soon imprisoned.
After proving her intelligence to the D'ni council by speaking to them in D'ni, they allow her to live in D'ni, but she is forbidden from returning to the surface, as they still do not trust her fully. She is sent to live with Aitrus and his family, who befriends her and promises to teach her more about the culture.
However, Aitrus' friendship with Ti'ana causes his friendship with Veovis to strain, due to Veovis' dislike of outsiders. Their friendship is tested when Veovis does not let Ti'ana link to Nidur Gemat for his Korfah V'ja ceremony and again when Aitrus mentions he is teaching her The Art. Veovis uses this information to get his linking books confiscated, though Master Kedri later presents evidence that allows Ti'ana to link and learn The Art. Their friendship Is eventually annulled after Aitrus proposes and marries Ti'ana, who eventually births Gehn (named after his paternal great-grandfather. It is around this time that Aitrus gives Anna her nickname "Ti'ana", which means storyteller in D'ni and references her multitude of surface stories she constantly tells Aitrus.
However, soon Aitrus comes to Ti'ana with a mysterious note and she suggests he discard it, but after another one appears, he goes to visit A'Gaeris behind her back, telling her he'll be working at the Guild Hall. However, a messenger comes for Aitrus while he's gone and Ti'ana figures out that he is not at the Guild Hall and goes looking for him, heading to K'veer. Aitrus comes home to an empty house and panics, though the two are reunited after Veovis returns her unharmed. Soon after, Veovis is convicted of murder (due to false evidence from A'Gaeris) and sentenced to a prison age.
Several years later, Gehn is appointed to the Guild of Book Makers and Ti'ana has second thoughts about him going, but Aitrus tells her it's the way of their world. She reluctantly lets him go after a trip to the surface and, though he is extremely homesick the first few months, he becomes determined after a speech from a master. Unfortunately, Veovis breaks out of his prison around this time (with the help of A'Gaeris) and blows up a bomb within the Guild of Ink Makers, causing Ti'ana to grow worried for her son and try to get him.
However, after she is refused entrance, she notices Veovis and trails him to Ederat, where she overhears Veovis and A'Gaeris take responsibility for the terrorism, threatening to overthrow D'ni. Veovis links out to find Aitrus and he tricks him into linking to Ederat, beliving that Ti'ana is held hostage there. They knock him out and place him in a cage, though Ti'ana is unsure who it is at the time. She ends up gathering supplies and Veovis' linking books before noticing Aitrus. She knocks out Suahrnir with a sleeping draught and tries to free Aitrus, but can't and promises to return for him. She is shortly caught by A'Gaeris, but is freed when a giant black bird attacks his face. Veovis chases after Ti'ana, but she sets his linking books on fire, as well as the door leading out and links back to D'ni, though not before Veovis manages to shoot her in the shoulder. The two appear in front of R'hira, who imprisons Veovis.
Several months later, Veovis is charged with his crimes and sentenced to be executed. However, Ti'ana speaks up for him and suggests imprisoning him and burning the linking books to it, telling The Council of Five that he isn't a bad person and was wrongfully imprisoned (due to a journal she found in Ederat that incriminated A'Gaeris). Veovis is sent to the age and the book is destroyed, though not before A'Gaeris manages to link in first.
At Gehn's graduation, Ti'ana begins to grow worried that Gehn is growing distant from her (though he is enamored with Aitrus). However, the ceremony is halted when a large gas spreads through D'ni, leading Ti'ana to evacuate with Gehn and Tasera to Gemedet. After a short while, Aitrus leaves to investigate D'ni, leaving Ti'ana and Tasera alone. Ti'ana frets over the safety of Aitrus and is surprised when he comes back a while later with a virus that killed off most of D'ni. He explains that D'ni was destroyed by Veovis and A'Gaeris, who used toxins to kill most of D'ni. After Tasera's death, Ti'ana, Aitrus and Gehn leave Gemedet, where he gives Ti'ana a map of the caverns and tells her to move back to the surface with Gehn.
As they're escaping, Aitrus hears a voice call for help and goes to investigate (which turns out to be Veovis, who was stabbed in the back by A'Gaeris and shortly after dies). However, A'Gaeris kidnaps both Ti'ana and Gehn and takes them to K'veer, where Aitrus is there waiting for them. Ti'ana watches as Aitrus links into a death book to trick A'Gaeris, who follows him into it, and she is devastated but emerges from the volcano at the Cleft shortly after, where she promises to make a new life for her and Gehn.
Book of Atrus
Eventually her son, always blaming her for their fate, left her. She stayed alone in the Cleft as a hermit making a living fro her small pool and garden. However one night about 10 years later, Gehn returned to her with his pregnant and ill wife desperately seeking her healing powers. After a long night she delivered the baby but despite doing her best, she was unable to save Keta. In his bitterness Gehn continued to blame her, and carelessly dug a grave for Keta spoiling her garden and pool, angering her. Anna offered to give him the baby, but Gehn was nonchallant, saying "You saved it, you look after it." Leaving his cloak behind, he left for D'ni.
She named the child Atrus after her late husband and raised him alone like a hermit, having contact only with caravan traders. She worked hard, growing precious herbs, finding rare minerals, carving stone figures or drawing iconic paintings. She traded them in return for flour, salt, cloth and other items that would help her and Atrus survive in the unforgiving desert.
She was very protective about Atrus and worrying that one trader might abduct him and sell him as a slave, she kept his existence secret, and taught him how to hide whenever the traders came.
She trained him to notice minute details and see The Whole and often asked him "What do you see?". She used to say to him to never be disappointed by his mistakes, but rather strive to learn from it.
Her death shattered Atrus' family. Atrus buried himself in work, spending less and less time with his sons, while Catherine was too consumed by sorrow to see that her sons needed her most. She held deep regrets for her death, and didn't write any more. Sirrus must have seen this as rejection, but didn't let it show, being proud even back then. Achenar never known how to channel his emotions appropriately.
Yeesha was never told about the circumstances of her death, but one day while she held Anna's picture, the Protector's necklace "talked" to her. Sad that her mother didn't write Ages any more, she 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.
Appearance & Personality
In her older years her face was gaunt yet handsome with fine gray hair tied back into a bun at the nape of her neck.
Anna possessed survival and healing knowledge allowing her to survive in the desert and also Gehn trusted her enough to seek help for Keta.
The traders considered her an old madwoman but admired her inventiveness and respected her strength and independence. Despite the great heat of the desert, she kept the hood of her cloak down, to show an air of strength and self-reliance. 
Anna used the space of the Cleft creatively, using every free surface as a canvas and decorated it.