Dungeons & Dragons dragons by age category:
0-10 Years: Basically a giant fire-breathing housecat. Has a big ego, but rarely plans beyond the next meal. Distract with something shiny.
10-100 Years: The firepower of a small army paired with the emotional keel of a somewhat sheltered teenager. Has grand ambitions, but makes poor life decisions; has probably fucked a bard.
100-1000 Years: Remember Smaug’s boast? The unabridged version from the book, not the cut-up version from the movie? Yeah, that. Legitimately scary, but not quite as clever as it thinks it is. Decent “final boss” material.
1000+ Years: A shapeshifting world-class sorcerer with superhuman intelligence, unlimited resources, and a lot of time on its hands. Some decide to impersonate gods; most are motivated primarily in terms of “hey, you know what would be hilarious?”. Distract with something shiny.