One of the funniest things about Possession is that A. S. Byatt isn't afraid to use totally un-subtle surnames to tell us a little something about a character's significance to the story.
Take Fergus Wolff, whose surname is just one letter away from being the word "wolf." In Possession's final chapter, Roland Mitchell describes Fergus as "a devourer" (28.192) —as opposed to a possessor, perhaps—and throughout the novel we see that he's a hyper-confident man who lives life in the fast lane. Maud Bailey found it absolutely overwhelming to date him, and Roland really hits the nail on the head when he suggests that Fergus is the kind of lover who can eat up another person's sense of self-possession and autonomy.
Like the rapacious wolf in Little Red Riding Hood and Into the Woods, Fergus is both charming and threatening. We see his charm when we learn that he seduced Maud at an academic conference by saying things like: "We two are the most intelligent people here, you know. You are the most beautiful thing I have ever seen or dreamed about. I want you, I need you, can't you feel it, it's irresistible" (4.163).
Later, we see his aggressive nature. Once he's caught a whiff of the discovery that Roland and Maud have made, Fergus confronts Maud in the basement of the British Museum, and is physically aggressive towards her, putting his hand around her wrist "like a handcuff" and refusing to let her go (12.225-36).
Like his wolfish namesake, Fergus goes on the hunt after he picks up the scent of Roland and Maud's discovery (not to mention their budding friendship/romance), and he's the one who tells Mortimer Cropper about the possible connection between Christabel LaMotte and Randolph Henry Ash.
Fergus gets his comeuppance by being dropped from the story after Chapter 17. Once he rats on Roland and Maud, he fades from view and never reappears in person.