Thread by @AlexandraErin

This is a setting detail, not a system detail.

(NB: Replies are open for replies to my answer, not to the question below. I have not asked how you feel about firearms in DND5E. On Twitter, your reply is supposed to be attached to the thing you are actually replying to.)

https://twitter.com/NevernotDM/status/1490309555166842881

Yep.

And these days as a game runner, I am for the most part of the mindset that the world can include somewhere any reasonable, approximately game-legal and approximately balanced thing a player wants for their character, because it's their fantasy, too.

https://twitter.com/masamage/status/1490379355771469824

Depending on my relationships with the players, I may take a firm stance on third party and homebrew options; specifically, if I have very differing levels of familiarity with them. "If it's in a WOTC 5E book, you can use it." is objective and treats everybody the same.

Whereas if two different people are bringing me their favorite third-party sub-class and I have to decide if I think either of them is too broken for the table, and one of them lives with me and the other is an internet pick-up... I don't want to do that.

But if you want your character to be an airship mechanic or a vampire slayer from a secret order of monster-hunting nuns... then airships and/or said secret order of monster-hunting nuns exist in the game's setting, as your character proves them to.

"So I can get bonuses against vampires by making up a backstory?"

No, you can get bonuses against vampires by taking appropriate mechanical options from those that are freely available to you. And if you want help making your character's mechanics fit their lore, I can do that.