I don't know. Thinking about it, I realized Opeth, nowadays, would probably do it in a way that would make it cool. I mean it doesn't have to be sword-and-sorcery, but dragons could be an excellent metaphor, just like lepers. Mikael could definitely do something with it that wouldn't be corny. Aren't Opeth great?
To each his own, but I don't believe fantasy can be pigeonholed as a child's genre as it has been by a few people in this thread. I'm sure a gifted/talented lyricist could go places with a fantasy concept and make quite a compelling album of it. Sadly, an example of such a feat escapes me presently, but I'll keep my eyes open