This title only has two items, "The Hero" and "The ... Blacksmith", so that wouldn't be an Oxford comma. I'm not sure if it's grammatically correct to add a comma between two items like that, but it does reduce ambiguity, so I guess it's fine.
- The title: "Abandoned: The Hero Who's So Strong He Breaks Every Weapon and The Elf Blacksmith" -> Without an Oxford comma (i.e. ", and The Elf Blacksmith"), it sounds like the hero breaks the poor elf blacksmith, too. Though I guess the lower-case "and" also helps against this interpretation.
I think it would be easier to just reorder the items for clarity (e.g., "The Elf Blacksmith and the Hero Who's So Strong He Breaks Every Weapon") but doing so might be considered unfaithful to the original title.