There is a small cave carved into the side of Da-Chao at Wutai. The fires in the cave block anyone from reaching the treasures at the end of the cave, but they can be put out with the right item. During your raid on Shinra's underwater reactor, Cloud and the gang can pick up the Leviathan Scales from a treasure chest on the dock. The scales hold the Water power of the summon Leviathan and will put out those pesky fires for good! Use the Leviathan Scales on each of the fires to find the Oritsuru Weapon for Yuffie abd the Steal as Well Materia.