To unlock a bonus section of the final dungeon, near the end of the game, equip an Elemental Spirit then speak to it in the Mana Village. Beat its quest to meet the Benevodon of the same element in another dungeon. Perform the same task for the other seven Elemental Spirits to get a total of eight Lex items. After beating the game, when the game resumes at the Mana Village, the Mana Tree mural will glow. Enter it to teleport to a bonus section of the final dungeon.