Here is my take on spell casting in the Dark Sun setting. I’ll be play testing it with some other Dark Sun material with my home group tomorrow night. Any and all feedback between now and then would be appreciated.
It uses the standard “Cast a spell” entry from the rulebook (page 144) and only adds in the two casting modes. I went this way because I don’t think it’s necessary to spell out setting-specific consequences in the move (except for defiling and preserving) because if we’re doing what we’re supposed to with DW, all of that will come from the setting and fiction anyway. THE thing that makes magic different in Dark Sun is defiling (and less powerful but friendlier preserving) IMO.