So, it's an often used myth: the heroes of the story arrive at an island in need of something important, and they discover that the island is actually a giant turtle. The heroes disturb it, and it dives.
But where does this myth come from? It sounds Greek or Persian. How would it fit into Ars Magica? And where?
I want to use it as a starting point for my new campaign. The characters are all survivors from a ship that went down in a storm, and are washed ashore on a strange island, which is actually a giant turte (why couldn't they just use this in Lost.. would have explained alot more. )
In medieval tales it's usually a whale that gets mistaken for an island, at least in the stories I've read.
At a guess I would say the stories originate from Greece. Medieval bestiaries almost all derive from either Pliny or Physiologus, again based on what I've read.
You could use this in any sea around Mythic Europe: the Mediterranean, Black Sea, Atlantic Ocean, North Sea, Baltic ... they all have whales. 8)
Sounds like the living island Jasconius from the legend of St. Brendan. ( en.wikipedia.org/wiki/Jasconius ) Two Fourth Edition Ars Magica books had material on this, Mythic Seas (a brief mention) and Living Lore.
It appears neither of my Carol Rose encyclopedias are on my bookshelf at the moment so I can't confirm any of this however I believe the Kraken had a similar mythological origin. I'm almost certain it showed up in Norwegian or Norse mythology.