I'm a senior, and I've heard my English teacher say this a million times, the purpose of the introduction is to introduce a claim/viewpoint. Yes, you can introduce the author, but that isn't the PRIMARY purpose. The hook goes at the bottom of the introduction, but also isn't the primary purpose. The topic kind of goes throughout the essay.
Introductions do include hooks and decide on a topic, but however, it is to inform the reader what your body paragraphs will be based on. It is basically like a trailer or teaser for a movie or show. You would include the 3 main ideas or the claim of the essay.
