The Pack screen is your access point to the draw packs for all of the tower dungeons available to you. Here you can select a pack and draw from it using either CP, crystals, or clear bonus points earned from clearing a dungeon. Drawing from a pack earns you a card which represents either a monster, or a piece of equipment (sword, shield, or ring). The more treacherous the dungeon, the greater the usefulness of the resulting card drawn. To see what cards are available in any given pack, simply scroll to the pack and touch the "Check Lineup" button.