Fridge Horror: It looks like a Happy Ending at first, and then the Fridge Horror sets in. Lirazel loved Erl because it was different from Elfland. In the end, it becomes part of Elfland. So now although she'll be with her family, none of them will ever be able to be content, because the entire country will be locked into changelessness. Elfland will continue its decline, and they won't even be able to communicate with the outside world thanks to the time dilation effect. No one is coming out of this happy, in the long term.