Creatures the active player controls attack this turn if able
While these are extremely plentiful when in print (you can easily walk down to your friendly local game store and buy one), securing the best possible price in recent years tends to require working with a distributor or waiting for a major sale on Amazon
Merlins protg arrives in play for just three ink and can quest for a modest one lore, but its in his ability to inspire others that Arthur, Wizard's Apprentice begins to show his potential as a standout in the set
Library of Alexandria You can only play Yawgmoth's Bargain in Vintage, but at least you can put four copies in your deck
For many others, you may just be gearing up for your first ever Prereleaselaying the groundwork for the first chapter in your Prerelease story
Similarly, once the third ability triggers, those creatures will get +4/+4 when it resolves, even if one or more of those creatures left the battlefield