Firstly, because Jeskai Elder has prowess, it automatically gets +1/+1 as Feat of Resistance is a noncreature spell
If X is 7 or more, you may play cards you own exiled this way until the end of your next turn.
Its the fastest of all mana rocks in the game
Much to my wife's chagrin, I tend to organize my collection via the "tossing the cards in whatever box happens to be nearby" method, which is not recommended
Some may hold fast to the position that these are different cards, but I cant shake the sense that Wizards effectively doubled the serialization count for a card in what I can only toss up to a problem of poor foresight
Notable card types are Shiko and Narset, Unified and Archmage Emeritus are a big part as they add both value and power, rewarding clever sequencing and strategic play