This is the most powerful rod in game and can only be used by Dagger. In order to obtain it you will have to advance Chocobo Hot and Cold as far as the Lagoon and the Ocean ability. You will also need to have dug up Chocograph #18 "Ocean". Equip this chocograph and head west of Everlang Island (Forgatten Continent) to dig up this Rod and a few other treasures.