In battles monsters will drop their "enemy card" which contains their status. Talk to Pios in your HQ in Shildia to put them in your "Enemy Cards Book". Every time you collect 10 different cards Pios will reward you with an item.

Book of Elders - Give Pios 276 Enemy Cards
Cosmic Disc - Give Pios 10 Enemy Cards
Philosopher's Scroll - Give Pios 276 Enemy Cards
Soul Scroll - Give Pios 200 Enemy Cards
Survival Book - Give Pios 100 Enemy Cards