Well, the first card that jumps out at me that seems like not only the biggest gainer but an early candidate to be the defining card of the format Courser of Kruphix was one of the most dominant cards in block, being a defining pillar of that format
Your opponent replies by chaining "Book of Moon", but because "Light and Darkness Dragon" has a Trigger Quick effect rather than a Multi-Trigger Quick effect, it cannot be used more than once in a chain and therefore cannot negate "Book of Moon's" activation
As cool as it is to cast this spell by discarding a plains card, casting it for 3 mana feels acceptable for a spell that hits two types of permanents
SE Secret Rare Magical Cylinders X TRAP Set 1 "Magic Cylinder" directly from your Deck or GY
The correct item name should appear in the purchase message, confirming that the cheat is working
You can't use more than one Lunar Cycle Ability during your turn