Staples Phyrexian Metamorph Neither Sculpting Steel nor Clone qualify as staples, but mix them together and you have a real winner
It not only replaces itself and can take out a creature thanks to deathtouch, it's also an evasive flier and an artifact creature, meaning it has plenty of synergies to work with
This card is an inexpensive way to achieve this effect, leading to some simple, easy wins with cards like Thassa's Oracle, Laboratory Maniac, and Jace, Wielder of Mysteries
It was a merfolk
Other people warped their mana bases and did massive damage to their decks to try and make good use of it, and many good players took far longer than they otherwise would have to recognize Zuran Orb due to the time they'd spent pointing and laughing at Dark Hearts
I wont really say much more about the Archenemy side of the Death Toll precon today that might have to wait for a more general discussion of these precons as a set