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Artorius Vigo was a Nilfgaardian mage and the uncle of Fringilla Vigo. It was he who introduced her to the mysteries of magic.

In the Blood and Wine expansion

While he does not appears directly in the "Blood and Wine" expansion, it is revealed that "Uncle Artorius" had created a magical land for young Annarietta and Syanna which they could access by uttering an incantation while reading a magic book.