The first wave of amass cards all created a Zombie Army, but with the addition of amass orcs in LTR, the original mechanic was changed to amass zombies. This allows different sets to represent armies that match the flavor of that set
It can also be 6/6 creature for only 4 mana once you have enough cards in the graveyard, with the ability to repeat its strong effect once it re-enters the battlefield and each time it attacks
Sheoldred, Whispering One and Rune-Scarred Demon are some of my favorites, but you can pretty much drop whatever pet eldrazi or demon you want and call it a day
It might not be as strong as Blighted Agent, but playing this on turn 1 into two Might of Old Krosas and a Mutagenic Growth have enabled many a turn-2 kill, and its solid even without the nuts
When I'm not playing Pocket, I'm diving into stores and ripping open packs in real life, hoping for excellent pulls of my favorite Pokmon