Erenplose / Dara Happa connection ?

I have been perusing an old tome which mentions the Iron Vrok is another name for the Roost of Tholm, the tenth piece of the Dara Happan imperial Regalia. That's food for thought and might give an interesting twist to my campaign.

We know Palangio, first age hero and servant of Nysalor, got his Iron Vrok from the depth of Erenplose city. He burst out of the water riding the Iron Vrok, rushed to Nysalor and proudly presented it to him. Later he was killed (by Arkat ?) and the Vrok / Roost was lost. The Vrok itself is some sort of big iron bird that can fly its master everywhere, including to the other side. It also protects him from all attacks.

My question : what is under the Mournsea that might have given Palangio a piece of the Dara Happan regalia ?? I'm interested in both any "official" info and any other idea, however bizarre, you might have. Philippe Sigaud ran part of his campaign in submerged Erenplose and made its few remaining inhabitants undying vampires, for instance. I read somewhere they might be brithini.

So what do you think of the Erenplose / Dara Happa connection ?