Drunar, Vile Overlord

When Drunar, Vile Overlord enters the battlefield, all other players exile half
of their nontoken creatures.
Pay{4}{p/b}{x}: Return X target creatures that were
exiled when Drunar, Vile Overlord entered the battlefield.
All creatures you control are vampires in addition
to their other types.
All vampires have flying and get +x/+x
where x is the number of creatures all opponents control.