There is portion in all the fairy realms that the fairy folks avoid to travel on. Not that this place is forbidden but more on the common knowledge that it is the region in the realms that does not abide by the usual rules or laws exercised by all fairies. If you are only too desperate to flee from all the realms you would be insane to search for sanctuary there. That is the case for the Dark Fairy. There is nowhere else to go but to the Dark Mountains and the rest of the treacherous zones beyond it.
The Dark Mountains derived its name from its dreary physical features as well as all the other shady and malevolent creatures inhabiting it like ogres for instance. The four realms living in a structured and harmonious way of life makes the Dark Mountain inhabitants shunned for their notoriety and disregard for rules and order.