Any definition of the word spelled the same way is legal
Crop Rotation, Deadly Rollick, Culling the Weak, Diabolic Intent, Phyrexian Altar, Ashnod's Altar, and Phyrexian Tower all play a big role in how the deck takes shape, creating several loops where creatures are sacrificed for benefits like infinite ETBs, death triggers, mana, and so on
This can only be done once per game, and is usually helpful if you draw a hand without many inkwell icons (which are used to play cards and use abilities) or containing too many expensive cards for the start of the game
Cards in the deck are independently strong since the goal is to play the strongest thing possible each turn, and synergies can make achieving that goal inconsistent
From Chocobos Paradise to the Kingdom of Alexandriapick up FFIX and follow along the protagonists in their journey across Gaia