This amulet is a quest item which Geralt receives from Dandelion in Murky Waters. Dandelion has brought a parcel from Triss and a letter. The parcel contains a Dimeritium amulet for Alvin which is supposed to help control his magical abilities and his constant nightmares.
Depending on Alvin's previous guardian, he will either be at the "fairytale ruins" outside the village where he will have to be rescued from the Gambling Ghost, or by the riverbank with a dog, where they are both threatened by a devourer (the only one you will ever see in daytime). It takes a little convincing to get Alvin to wear the amulet:
Alvin: Necklaces are for girls!
Geralt: It'll keep your nightmares at bay. I wear one.
Alvin: An amulet like yours!
However, it is not strong enough to keep him from prophesying once again. "... look into my eyes d'hoine... you are not even human... now do you see the necessity..."
Associated quests
Notes
- At the end of the game, Geralt finds (to his surprise) that the Grand Master also wears such a pendant.