I figure that now that you have the airship, you will want to explore. Be my guest. When you are done, Toria is northwest of Baron. In Toria you learn that you cannot fight in the Dark Elf's cave with metal weapons. I say that you should keep your strongest equipment on, and run from every fight. That saves you money, and gets you through the cave faster. But if you need the fights, go ahead and buy the crappy equipment. In Toria castle, you will find Edward. Get out of the castle, go straight up to get a Black Chocobo, and then go East to get to the cave. Be sure that you take the silver ring off of Yang (if you even got it), or any metal on Yang (his claws are ok). Make sure to keep one person without metal on. Also, make sure you get the harp from Edward.

Just go through the cave. It's pretty short. When you get to the Dark Elf, he talks in ALL CAPS . For the first fight, you will come close to dying. Then Edward talks to you with his harp. It destroys the elf's metallic barrier. If you took my advice earlier, just run up to him and start the fight. If you didn't, equip yourselves, and then go up and fight him. In his first form, he just uses some crappy attack. But when "ME CHANGE," he does D. Breath, and that sucks. Whenever you win (assuming that you will), you will get the Crystal. Leave the Crystal Room, and then use Exit. take the Crystal to Toroia. Kain tells you to take the crystal out to your airship. Go to the treasure room and get all of the treasures. Now go to the Airship.