What is witcher 3 crystal skull?

In Witcher 3, the crystal skull is a quest item that is obtained during the side quest "The Lord of Undvik." It is said to be the skull of a powerful mage who lived during the Conjunction of the Spheres, an event that brought magic and monsters into the world of The Witcher.

When Geralt first obtains the crystal skull, he cannot yet discern its true power. However, during the course of the quest, it is revealed that the skull has the ability to amplify magical energy and create a powerful explosion. In the hands of the wrong individual, it could bring great destruction.

The crystal skull becomes an important item for completing the quest, as it is needed to defeat the creature known as Hjalmar's Giant and access its lair. After completing the quest, the crystal skull can be kept as a unique and powerful item in Geralt's inventory.