Daenerys Targaryen

When Daenerys Targaryan enters the battlefield,
create Rhaegal, a 4/4 blue Dragon creature token
with flying, Drogon, a 4/4 red Dragon creature
token with flying and Viserion, a 4/4 white
Dragon creature token with flying. You become
the monarch.
When Daenerys Targaryen leaves the battlefield,
exile all dragons.