Back in WC09 and before, you'd have to beat the CPUs each about 5 times each in order to unlock a new pack
The Reaper, King No More The original Reaper King is a Scarecrow lord, but his retired version is a Jund value engine
Sometimes your opponents flip over two or three on color bombs while you never see key cards your deck is looking for
Because the range of Modern decks that get played is so wide, having a straightforward plan to punish weak hands, bad plans, or stumbles is valuable, and a few 4/4s with trample will end games quickly against an opponent who is unprepared
These unlock relatively soon, around level six, and are a way for you to show off cards that you've collected as shown in Austin John Plays' YouTube video
It can even protect itself from destruction by battle