The cast of any Myst game is limited, since the spotlight is devoted to exploration, and each age has such individuality that they could be characters in their own right. Nevertheless, some more conventional characters also make an appearance, providing necessary context, direction and, most importantly, conflict.
Atrus: For all intents and purposes, he’s the face and voice of the series. As you gradually find out, both from the games and the books, Atrus is part D’ni: a long-lived race of human-like beings who created the Art of writing linking books. A sizeable chunk of their population ended up on Earth using this very method after discovering that their homeworld was dying, and settled in a very large underground cavern somewhere in New Mexico, where they built a city named after themselves. Atrus’ grandfather was D’ni, but his mother and grandmother were human. He himself married a non-D’ni woman and had two sons with her, Sirrus and Achenar, both named after stars. Portrayed by one of the creators of the game, Rand Miller, Atrus appears as a middle-aged man with sad eyes, small round glasses, light brown hair and a beard. You don’t see much of him, but he comes across as a kind, bookish, caring person who has been struck by disaster and is trying his best to find a solution. Explaining any more at this point would be a spoiler, but suffice it to say that he’s the good guy. He has a habit of writing journals detailing his explorations, and those will be your guides to the four ages you visit in the game.
Achenar: Atrus’ elder son is imprisoned in the blue book. He is his father’s prime suspect, and, from the get-go, it’s pretty clear that he’s not all there. Appearing as a dishevelled man with bushy brown hair and a beard (he’s also portrayed by Rand Miller), and a generally wild look about him, he punctuates his speech with giggles, rants and mood swings. He also very adamantly states that his brother is a greedy bastard who tricked Atrus into wrongfully imprisoning him. Three of the ages you visit have a room where each brother lived, and Achenar…well, let’s just say he has some very peculiar tastes in both interior decoration and entertainment.
Sirrus: Atrus’ younger son is, you guessed it, languishing in the red book. He’s very different from his brother, appearing as a well-mannered young man, with short brown hair, a neatly-trimmed goatee and mocking eyes (he’s portrayed by Robyn Miller, brother to Rand and co-developer of the game). He comes across as shrewd and reasonable, if somewhat haughty, and asserts that his brother is a raving lunatic, while he has been wrongfully imprisoned. I’m seeing a pattern here. Just like Achenar, Sirrus also has his own quarters in three of the ages you visit, each a prime example of lavish interior decoration. Among other things.