The Arkenstone
The Hobbit: On the Doorstep#20 (x1)
Treasure
[0]

Attach to a hero.

Action: Exhaust The Arkenstone and raise your threat by X to lower by X the cost of the next ally you play this phase that matches the attached hero's sphere.

"...the Heart of the Mountain; and it is also the heart of Thorin. He values it above a rive of gold." –Bilbo, The Hobbit