I've heard Windstones can take Pirates to the many worlds of the Spiral, if they acquire them. How many are there right now, and how do I get them?
Windstones will be made available when they are needed. Just follow the story line and you will get them when you need them (usually just one at a time and not in stores!). Not sure how many there are now but I am certain that there is one per each Spiral World.
Windstones are only given out through main quests after you have completed each world's main quests, you will get a windstone to the next world. You'll see many storm gates you cannot use because you havent gotten to the world, or the world has not been put into the game.