Amalgamation of Flesh

As an additional cost to cast this spell, sacrifice
any number of creatures you control.
When Amalgamation of Flesh enters the battlefield, creature X 1/1 black spirit tokens with flying, where X is the number of creatures you sacrificed to cast Amalgamation of Flesh.
Amalgamation of Flesh's power and toughness are equal to the total power and toughness of creatures you sacrificed to cast Amalgamation of Flesh.