The Book Of Ti’ana takes place earlier than The Book Of Atrus. The first part of the book focuses on the life of Atrus’s grandfather, Aitrus with his parents, Kahlis and Tasera, Aitrus’s meeting with Ti’ana and the birth of their son, Gehn.
The book also explains the destruction of the D’ni civilization. Two D’ni – Veovis and A’Gaeris – plot to destroy their civilization, which they believe has been corrupted. Veovis and A’Gaeris create a plague which wipes out many of the D’ni and follows them through the Ages.
Veovis is murdered by A’Gaeris for refusing to write an Age where the two of them would have been worshipped as gods, and Aitrus sacrifices himself in order to lure A’Gaeris into an unstable Age, killing them both.
In the final scene, Atrus’s grandmother, Anna, settles in the cleft near the volcano, where we first met her at the beginning of The Book of Atrus.