The effects of feeding Choco a Dead Pepper are different according to terrain. They can be used to seek out hidden treasures by drilling the cracks on sides of mountains, the bubbling waters in the sea, and fly up into the Chocobo's Air Garden. They can also be used in battle to deal 30 damage for every Dead Pepper in the inventory. Dead Peppers are supposedly named as such because the fruit that bears them has died due to Mist.