Received from: Zyvik
Step 1: Talk to Dethmold about Henselt's medallion
When you ask Zyvik about the details of the war, you will learn of Crest's medallion - it's worth to deep digger into the matter and learn the details of its further fate. You will learn that at the moment it's in Henselt's possession. Head to Dethmold (M25, 7) and talk with him about the King's medallion. Unfortunately you won't receive it until you lift the curse.
Step 2: Take the curse off of Henselt and return to the medallion matter
Unfortunately after you lift the curse, Henselt will be attacked by the assassins - you have to learn everything about their intentions and only then will you receive the medallion.
In order to continue, you have to finish The Blood Curse and The Assassins of Kings.
After you finish the mission connected with the assassins, Dethmold will give you the medallion.