"Malý amulet vyrobený z kousků modrého kovu".
This amulet is a quest item which Geralt receives from Marigold in Bahnice. Dandelion has brought a parcel from Triss and a dopis. The parcel contains a dwimeritové amulet for Alvin which is supposed to help control his magical abilities and his constant nightmares.
Depending on Alvin's previous guardian, he'll either be at the "fairytale ruins" outside the village where he'll have to be rescued from the Gambling Ghost, or by Říčka with pes, where they are both threatened by a požíračky (the only one you will ever see in daytime). It takes a little convincing to get Alvin to wear the amulet.
However, it is not strong enough to keep him from prophesying once again.
At the end of the game, Geralt finds (to his surprise) that the Velmistr also wears such an pendant.