Hecatomb
Ice Age — rare
Enchantment
Hecatomb rulings:
2004-10-04: If you have less than 4 creatures, you do not partially sacrifice. You pay 4 creatures or none.
2004-10-04: The sacrifice is done as a triggered ability just after it enters the battlefield. It is not done on casting.
2004-10-04: You choose whether to sacrifice creatures or not on resolution. If not, then you sacrifice Hecatomb. You can choose to not sacrifice creatures if you no longer control this card on resolution.