Why this is a good card to keep in your deck is that there are many characters, items, and actions that allow you to look at your top card, or cards, and return them to the deck
I believe an early version of this card experimented with each Zombie getting to give -1/-1 to target creature until end of turn, but that ended up being too powerful, and the spell would often decimate the other side when cast late in the game
How Does Double Strike Work on Planeswalkers
You will need at least a 2/2 Ballista to start the loop, since it doesnt get the +1/+1 counter returned fast enough to stop it dying if it goes down to 0/0
Then again, if you leave out the one-of-a-kind cards, completing a full set of all real human photo cards seems fairly doable, which is nice