Pirate King's Treasure Chest

Pirate what's wasserwha?
Is there more areabosses?

He spawns in the same maps as Eregos used to, as far as I can tell. (Cassandra only gives general areas, not the detailed map like with Eregos) I don't know how often nor during which hours of the day.

And that bit about your level - as true as it was for Eregos, meaning, utter bull. Got boxes at Golem Temple, got the scrolls out of them, too. Got the exact same boxes at ToT (they stack), all junk.