Just a thought: Can Two-Edge have children? A lion and a tiger can have offspring, but the offspring can't offspring. Is it the same way with elves and trolls? An elf and a troll can - with some magic - have offspring but the offspring can't have offspring. And yes, I know that Timmorn, the offspring of an elf (High One) and a wolf was definitely able to have offspring, but that might have something to do with the fact that Timmain had actually transformed into a wolf when Timmorn was born.