The protective jewelry is given to Finn and Jake by Princess Bubblegum in "Mortal Folly." Princess Bubblegum (and possibly other princesses and royalty in Ooo) wears this jewelry. The protective qualities of the jewelry are seemingly in the gemstones. The jewelry grants the wearer protection from the Lich's powerful spells, most notably his ability to control minds. Finn's jewel breaks during his encounter with the Lich, almost causing the Lich to gain control of Finn. However, Finn is protected by the power of "liking someone a lot" infused in the sweater Princess Bubblegum made for him.