An aristocrat who raised and kept Nastasya as a mistress, Totsky now wants to marry her off to Ganya in order to protect himself.
You know what's strange? How Totsky totally disappears from this novel. You know, he starts out like all the best mustachio-twirling villains, all full of sexual depravity and zero moral fiber—compare him to other similarly degenerate aristocratic evil-doers like Lord Steyne from Vanity Fair, the Marquis St. Evrémonde from A Tale of Two Cities, and of course, everyone's favorite, Count Dracula. And that backstory? Yikes. He picks up a young orphan girl, raises her to adolescence—gotta love those totally lax orphan laws—and then just like that, forces her to be his mistress, forever ruining her chances of living a normal life.
Ordinarily, a character like this would either get his just desserts (in a Dickens-style novel where all the characters either get presents or coal in their stockings), or maybe end the novel sneering from the sidelines (in a satire where evil triumphs over good, "because good is dumb" as Lord Dark Helmet has it in Spaceballs). In this novel, though, the most dastardly and palpably evil of all the characters (seriously, even Rogozhin gets a few passes here and there) simply goes away and is never heard from again once the action starts. Why do you think Dostoevsky removes him from the scene? What would be the effect on the novel if he were in Pavlovsk?