Howdy, you are the last sliver of dragon DNA. After thousands of years of being extinct, you've managed to infect one random human who was spelunking. Your goal and reason for being is simple. Transform the entire human race into intelligent yet savage dragons, and while you're at it, maybe turn birds, and other animals were applicable into non-sapient dragons like creatures who can fulfill the same nitch in the ecosystem. No strand of DNA on the planet will be left untouched.
But you have to be careful, cunning, cautious, and patient. Going full tilt right away will only lead to swift and brutal reprisal. The more converts you can get than corpses, the better. Mutate reptiles into adorable pets who will unwittingly spread you to humans across the world? Incubate in the wild? You don't pretend to be the hero here.
The choices are yours, but the goal remains absolute, mutate the human race into a species of scaled flying thinking savage reptiles.