My Name Is Legion wrote:
Well, he's a character who makes rather a deal out of "I have returned..." but he's alleged to be a new character. There certainly is no indication so far that he's familiar to Kirk and his crew.
Let's chew on that for a bit.
Nothing to chew on. There are tons of stories about characters returning somewhere they've been before in-universe even though it never came up in the specific work of fiction before. Heck, "Space Seed" itself was about Khan "returning" after having been presumed dead. ST:TMP was about the return of a space probe that nobody in the audience had ever heard of until it was revealed in the movie. Lord of the Rings
was about Aragorn returning to claim his crown, even though we never saw his initial reign. The audience doesn't need to have prior familiarity with a character in order for a valid story to be told about that character's return. All that matters is that the other characters are aware of the history.