"Do you really wish to know?" — Spoilers from the books and/or adaptations to follow!
Newboy's talisman is the subject of a bet between the Crinfrid Reavers and an unnamed nobleman. Newboy has bet that with this talisman, he can go into battle without armor and emerge unharmed.
The medallion is cursed. After Anezka performs her ritual, the talisman is transformed into Melitele's Heart and its powers are restored.