Start off this mission by talking to any of the gate guards located in Windurst. They will ask you to accept a mission; do so, and then the guard you spoke to tells you to go to the Orastory in Port Windurst. When you head there, its right by the Shiva Gate, talk to any of the two Taru Tarus located on the stage, and another cutscene will ensue. You will be asked to go to the Horutoto Ruins and find one of the Taru Tarus. Head over to East Sataburata, and go to the entrance to the Inner Horutoto Ruins. Head inside, and go down the ruins. If you follow the path, and into the large square room, follow along until you find a gate, where you will see another cutscene. The Taru Taru in the cutscene will ask you to find a cracked spehere in one of the Magical Gizmos located in the dungeon. It is usually the last Gizmo you check, so once you have found searched all the Gizmos and found the cracked orb, head back to the Orastory, and the quest will be completed.