The age of fire is at its end.
More and more get cursed with the Darksign and lose their sanity, only to life forever as mindless husks.
Those who are branded with the accursed Darksign are called the Undead, and they get carried of to the Undead Asylum, a prison of cold stone far, far away from all of civilisation located upon a lone mountain.
There are no guards, for there are only the insane hollows there and those who will be insane before long.
No one can escape from the asylum, because none are able to climb down from this peak, because the wings of those who should be able to fly lose all their feathers, because the horns of those who should be able to use magic turn into nothing but dead bone.
Those cursed souls will spend the rest of eternity in this cold, damp prison.
This is your fate.
Fluttershy.