Cheapest priced copy (Murders at Karlov Manor): $2.79 at Card Kingdom, near mint, their price list as of .
Slime Against Humanity 
Sorcery · Common · Murders at Karlov Manor · #177
Create a 0/0 green Ooze creature token with trample. Put X +1/+1 counters on it, where X is two plus the total number of cards you own in exile and in your graveyard that are Oozes or are named Slime Against Humanity.
A deck can have any number of cards named Slime Against Humanity.
Legal inCommanderBrawlStandardPioneerModernLegacyVintagePauper
4 printings · $2.79 to $449.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Murders at Karlov Manor | 177 | Common | $2.79 | $4.49 |
| Secret Lair Drop | 7077 | Rare | — | $229.99 |
| Secret Lair Drop | 7078 | Rare | — | $229.99 |
| Secret Lair Drop | 7083 | Rare | — | $449.99 |
4 rulings from Wizards of the Coast
- 2 February 2024The last ability of Slime Against Humanity lets you ignore the "four-of" rule. It doesn't let you ignore format legality. For example, during a Murders at Karlov Manor Limited event, you can't add Slime Against Humanity from your personal collection.
- 2 February 2024If you own face-down cards in exile, they won't count toward the value of X, even if you're allowed to look at them and you know they are Ooze cards or cards named Slime Against Humanity.
- 2 February 2024The last ability of Slime Against Humanity also lets you ignore the "singleton" rule in formats like Commander.
- 2 February 2024Slime Against Humanity isn't put into your graveyard until after it finishes resolving, so it doesn't count itself for its own effect.