I was using Seoni and was in combat against a Grazuul, on the Wooden Bridge location, Sandpoint Under Siege scenario, normal difficulty.
I rolled my combat and only got an 11, and the check was 16. I had the Sihedron Medallion in my hand, but couldn't use it. It had a lock on it. So I had to discard 5 cards total, and couldn't discard the Medallion to reduce damage by 4.
Is this a bug? Or am I missing a rule somewhere?