Alduin, World-Ender

Flash, flying, menace
When Alduin enters the battlefield, sacrifice any
number of creatures you control. Create that
many 4/4 red Dragon creature tokens with flying.
{4}{u}{b}{r}: Return Alduin, World Ender from
your graveyard to the battlefield.
Alduin, Bane of Kings, ancient shadow unbound,
with a hunger to swallow the world.