Keiji Inafune's Soul Sacrifice, as the name suggests, forces you to give up things, from items you find to parts of your own body, for power. Speaking with the PlayStation Blog, he suggested that not only does it force you to consider everything you do carefully, it also has the potential for enjoyable back-and-forth with other players.
"When you're playing together with your friends, it could be entertaining because it creates a new dialogue," he said. "If my character is dying, and my friend decides to sacrifice me, I might say 'hey, what are you doing?! Don't sacrifice me!'"
Your choices, depending on how often you choose to sacrifice or "save" creatures, will affect your appearance, as well, in the expected ways. "So if you keep on saving, or keep on sacrificing, the visual effect will look different," Inafune said, "you'll look more angelic if you keep saving, more evil if you keep sacrificing."