Heroic Purpose

Your name is destined to become legend and you have prepared yourself for the greatest foes. You gain the following benefits. 

Legendary Challenger.  Immediately after a creature you can see expends a legendary action or legendary resistance, you can use your reaction to make one melee attack or ranged attack with a weapon against that creature. You can use Legendary Challenger a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest. 

Threshold of Victory. When a legendary creature is bloodied, you and any ally within 30 feet can gain heroic inspiration.