A Thunder of Dragons

Search your library for up to one Dragon of each
color (white, blue, black, red, and green) and put
them into your hand. If you have a Dragon of
each color in your hand, you win the game.
Otherwise, put all Dragons from your hand into
exile face down. You may play them for one
mana of their respective color(s).
"Did you know that a group of dragons
is called a thunder? Well, now you know why."