Splitting Slime is a rare Creature — Ooze card from Conspiracy: Take the Crown (CN2), collector number 72. Current market price: $0.87 (foil $2.42), TCGplayer market prices via Scryfall.
{4}{G}{G}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.) When this creature becomes monstrous, create a token that's a copy of this creature. (The token has no counters and isn't monstrous.)