"The rules are pretty simple. The first person posts an idea for a card, but
without a casting cost. The next person provides a casting cost for that card
(repost the card's effect so we can see the completed card), and posts an idea
for a new card (without a casting cost). You may include the color and rarity
in your card idea if you want, but it's not necessary."
I found this on Salvation and it looked fun.
I'll start.
Rise of an Army
Sorcery
Exile all Creature cards in your Graveyard, then put a 2/2 Black Zombie creature token onto the Battlefield for each creature exiled this way.