Instructions
Tap the "Challenge Mode" button on the "Yu-Gi-Oh! World Championship 2007" main menu. This brings up the different challenges you can complete to unlock better cards and booster packs for your deck.
Tap the "LP Survival" option. If you have not unlocked this already, you must defeat all of the Level One and Level Two duelists five times each to unlock it.
Tap the "Infinite" option in LP Survival. This mode pits you against duelist after duelist until you lose a duel, which potentially can go on forever.
Defeat 15 duelists on Infinite mode in LP Survival to unlock the "Spellcaster Collection 2" booster pack. Once you complete the challenge, the pack will be available in the "Duelist Menu," which you can access via the main menu.