Soul Scroll
Simply give Pios 200 different Enemy Cards.

Book of Elders
Simply give Pios 276 different Enemy Cards.

Cosmic Disc
Simply give Pios 10 different Enemy Cards.

Survival Book
Simply give Pios 100 different Enemy Cards.

Completion bonus
Finish the game completely, then load your saved game. You will start a new game with every item, level, and gold attained. However, enemies will be even harder.

Old Town Way mission: 100% kill rate in the ambush
It is feasible to obtain a 100% kill rate in this mission. Just prior to you approaching the final group of enemies in the lower right corner, do not get near them with your main character. Instead, place your main character as far away from them as you can then send your second character over just near enough to have them pursue him or her. Then lure them to where your first character is waiting and kill them. After that, finish the stage with the battle with the main Boss. Hopefully you killed all of the other enemies, you will receive a 100% kill rate when your at the reward screen.