Invade the City is a uncommon Sorcery card from War of the Spark (WAR), collector number 201. Current market price: $0.20 (foil $0.39), TCGplayer market prices via Scryfall.
Amass Zombies X, where X is the number of instant and sorcery cards in your graveyard. (Put X +1/+1 counters on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)