You're Dragonborn

As an additional cost of playing this card, there must be X dragons in any graveyard.
{1}, enchant target Legendary Creature. Creature gains the Dragonborn Type. Place X Dragon Souls counters on enchanted creature, and add 1 counter for every dragon who is defeated while this card is on the battlefield. Remove a Dragon Soul counter to play a Thume free.

"The old tales tell of the Dragonborn who could kill dragons and steal their power. You must be one!"
- Whiterun Guard