The Dragonborn Comes

Enchant target creature only if it's legendary.
Equipped creature add Dragonborn as a type.

Every time any legendary creature controlled by an
opponent dies, put a level counter on this creature.
This creature gets +X/+X where X is the number
of level counters on it.
Every time a Dragon legendary creature dies, you
may add a Shout card from your library or
graveyard to your hand.