Today I. Will tell you how to catch some rare fish. To catch marlin complete the mission that you make fish bait To catch the fish that lives only in mysterious places go to the ancient grove and fish in one of the ponds. The fish that has been around since ancient times can be found in the kunka ruins and near the end of rune valley (in the pond near the entrance to kunka ruins) Marlin and ancient fish are required for quests.
k heres a hint for you get past the dunes you must help a dog get the staff of sand, In order to find the legendary flower you must go to the ancient grove through the rune caverns.After you find it you must then go to the ANC world