In Myst IV: Revelation, you can finally learn the fate of Sirrus and Achenar - the two villains first introduced in the original Myst.
The brothers remained trapped in separate prison worlds, abandoned by their father for the crimes they had committed. You must now venture deep into these worlds, while uncovering the mystery surrounding the disappearance of a little girl.
By solving puzzles, taking photos, and interacting with other characters, you'll soon understand the villains' motivations.