For the maps with hidden treasures, you must obtain the treasure on the first playthrough of the map. Otherwise, on a second attempt of the map, the treasure will be downgraded to easily obtainable items such as Hide Caps, Mage Oils, and Herbs.
Unlock the following bonus battle maps by performing the corresponding tasks:
MAP - HOW TO UNLOCK Avery Fields - Examine the well at the top of the Church of Restoration during your second visit. Foreign Quarter - Examine the barrel to your left at the start of the Biruni University stage. Four Swordsman Spring - Examine the hollowed out tree at the dry riverbed. Gillbaris Gardens - Examine the skeleton on the opposite side of the central tree from the chest in the Timion Vale mission. Halls Of Atonement - Examine the king's throne in the Royal Courtyard. Keliask's Tomb - Examine the glimmering tablet on the ground in the ancient ruins. Ragnar's Gorge - Examine one of the crates during the mission in Tolby. Trivishim's Corridor - Use the second mine cart in Dread to open up a cave entrance. Wanderlust - Beat all story and optional battles two times.