Student or Learner
Nick shot another look at me. “Used my powers. Figured that made more sense than attempting hand-to-hand, you know?” Something crackled against my skin like electricity, and Daisy’s hair ruffled. There was a distant look on Nick’s face as he continued. “One of the guys caught me as I was trying to get out a win¬dow. He had this black knife.” The china on the table began to rattle, and I saw Kristopher and Elizabeth shoot each other worried looks. “I didn’t know what demon¬glass was then,” Nick said, “but I knew it hurt like a moth—” ??
what is moth? moth bug or moth.... what?
I *think* the reason there's a dash there is that he's breaking off mid-word, and the word he was in the middle of saying was (please excuse me for saying this) "motherfucker".
To hurt like a motherfucker is (very unpleasant) colloquial expression for hurting a great deal. You will also hear "hurt like a bitch" and various other obscenities.
At a guess, since it's a child's novel (or at least one aimed at teenagers) it's the author's way of implying a swearword for realism, while not actually having to use it and risk offending people.