I'm making a character for an upcoming D&D 5e campaign who is secretly a dragon who permanently polymorphed itself (so, no mechanical advantages, just story background). Wondering what background would best reflect the fact that - rather than having a typical human upbringing - my character spent the first hundred or so years of his life as an avaricious fire-breathing gold-hoarding dragon before deciding, for reasons of his own, that being smaller and friendlier was better. My DM is open to homebrew content, so if there's something out there already or modifications that could be made to an existing published background that's fair game. I thought about maybe modifying the flavor of the Noble background, but mechanically I'm not sure if there's something that makes better sense.
The Charlatan background comes to mind as likely your character would have had to create an identity from scratch to blend in with society.
** Trait – False Identity
You have created a second identity that includes documentation, established acquaintances, and disguises that allow you to assume that persona. Additionally, you can forge documents including official papers and personal letters in a specific person’s handwriting, as long as you have seen an example of the kind of document you are trying to copy. **