Bring it in against an opponent who has multiple good targets
These are cards with upkeep costs that cumulate over each turn, as the name implies
However, you can consider playing fewer than four copies of a card if: It gets worse in multiples (such as legendary creatures) It's only useful against certain matchups It's a win condition, and your control deck will have time to dig through the deck and find it You're stuck choosing between two cards which have equally strong, similar, but slightly different effects (you could play two of each) It's a slightly worse version of a card you have four copies of already, and you're including it because you want even more of that effect
Do note that as an endgame piece, Craterhoof Behemoth comes with a very steep cost (5GGG), so you may want mana generation cards to catch your opponent off-guard before the 8 th turn
One of the reasons it has managed to outlast other card games is that it has managed to stay interesting by adding new cards, including special crossover packs that draw from other popular media