When do we finally see Smaug? Despite the narrator’s omniscient knowledge of Middle Earth, why do you think the narrator saves the full description of Smaug until Bilbo sees him in the Lonely Mountain?

Bilbo finally sees Smaug in chapter 12. Even though the narrator is omniscient, it is Bilbo who we are largely following so it makes sense that it is with Bilbo when we fully experience the magnificence of Smaug.