I'm a helper DM for a West Marches style of game, using a heavily homebrewed setting and mechanic set.
One of our prospective players has a character concept that simply cannot work with the setting at all, mostly due to being from other settings (and thus implying dimensional travel and setting crossovers that we're not comfortable with, even without knowing what those other settings are).
- Trying to talk them into adapting the character to this setting without the external attachments and backgrounds was rejected because the character 'wouldn't be worth playing without them'.
- Naturally, I suggested they try a different character concept, but their response was that they only have any interest in playing this one character and do not want to play what they call "a throwaway character".
- I suggested that they find a different game in which they could play this character, but their response is that they want to play in this game.
I am at a loss here. I won't be budging and allowing the original concept, but they're also not budging on any of these three points. I could ultimately tell them to get lost until they have another concept, but that's a last resort, as I'd rather convince them to try a new concept here.
Those of you who have dealt with this particular type of player, how did you get them to try a new concept?