Katran (or Catherine, Katran is her Rivenese name) was a native of Riven who met Atrus there and eventually escaped to Myst Island and became his wife.
They had two sons, Sirrus & Achenar who subsequently tricked Katran into going back to Riven where she became stranded and ended up being imprisoned by Atrus’s father Gehn.
Katran was extremely gifted in the art of writing linking books and it was she who repaired Gehn’s faulty age of Tay so that the Moiety rebels had a place of safety, Tay eventually became a refuge for all of the Rivenese people.
With Katran trapped on Riven and Atrus having to stay and repair the age as best he can it falls to the stranger to rescue her before Riven collapses, the stranger also has to trap Gehn in a prison book in order to rescue Katran .
Katran was played by Sheila Goold (Voiceover by Rengin Altay) who has a number of acting credits to her name and is still active on the acting circuit.