Aliens vs Dragons

At the beginning of your upkeep, choose a player.
That player sacrifices a creature. If they can't,
they discard a card and lose 3 life.
At the beginning of your end step, if an
opponent has no creatures, create a 6/6 Black
Alien creature token with deathtouch. If an
opponent has no cards in hand, create a 4/4 Red
Dragon creature token with flying.