If you control no monsters in your Main Monster Zone: Each player sends the top 2 cards of their Deck to the GY (or as many as possible, if less than 2), then, if you sent at least 1 card to the GY, and have 3 or more Spells in your GY, you can shuffle all your opponent's monsters from the Extra Monster Zone into the Deck.
That might not seem too impressive to the casual eye, but building a deck around their abilities can bring a world of hurt, and cute Eevees, to your opponent
Wed certainly lose a large number of the people who make the game special today
Will Arrive in Time for Christmas
Therefore, running three of these is a must
7 Akroma's Memorial There are few better cards for giving your army trample than Akromas Memorial