Both Slivers and Elves got their own similar pools of Bonus cards, given out with a range of different drops
Charizard (001/015) Charizard is usually the most expensive card in a set, but surprisingly, this is not the most valuable Dragon Discovery card
To make matters worse (or better, depending on your viewpoint), Agent Frank Horrigan is indestructible on attacks, making it well worth your 7-mana investment
Aetherdrift Aetherdrift play boosters is a tough one, because just like a race, there's only one winner and if you have 10 guilds racing like this set, nine losers
This goes up a bit as well based on how much of an improvement having this is to the ability to keep a hand meaning most mulligans will occur on hands without this in them
Giants are the biggest losers of ECL because they had the most to gain and gained the least