Atlantica should be open to you after you've completed Agrabah. Although most times before you can reach the junction between your choice of Halloween Town or Atlantica, Monstro will interrupt your course and swallow you but you can transport back to your Gummi Ship at any time to visit Atlantica.
It is all chance of what card you will get from a battle
You find all your answers for Kingdom Hearts on "wiki Kingdom Hearts"
Kingdom Hearts- Air Pirate, Battleship, Pirate Kingdom Hearts II- Aerial Knocker, Shaman.
There are no Gameshark codes for Kingdom Hearts 2.
Hot Topic, You can go on-line at hottopic.com and search kingdom hearts and there's a kingdom hearts necklaces and other things.
You have to earn them.
There is no possible way of finding Xemnas in kingdom hearts. You are only able of finding him in kingdom hearts 2, which he is the last boss in the game.
You can find Kingdom Hearts in: * Gamestop * Wal-Mart * Best Buy Hope this helps! =)
Kingdom Hearts backpacks, shirts, and other accessories are available at Hot Topic.
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U cant really find all the treasures at one place. For the places of all treasure chests look in www.gamefaqs.com