The Dragonborn, Alduin's Bane

Ward {2}
At the beginning of combat on your turn,
pay {w}{u}{b}{r}{g}. Legendary creatures you control get +X/+X until the end of combat, where X is the number of your experience counters.

Whenever a dragon is put into a graveyard
from anywhere for the first time each turn,
you get an experience counter.