Ostrit

Ostrit was a magnate at the court of King Foltest in Vizima. He loved the king’s sister Adda, and when her relationship with her brother led to a pregnancy, he is the one held responsible for the curse that followed. Whether the curse was really his doing or came from their mother, Sancia, who also opposed the affair, is never settled for certain. Adda died giving birth, the child was buried with her, and years later the girl rose from the crypt as a striga.

In The Witcher

Ostrit is long dead by the time of the game and appears only through his journal. In the main quest Her Highness the Striga, Princess Adda has turned into a striga again, and Geralt follows the trail to the chapel at the Vizima Swamp Cemetery. There, in Adda’s sarcophagus, he finds Ostrit’s journal.

The journal makes it clear that the relapse was no accident: someone used its contents as a template to renew Adda’s curse. That someone turns out to be Count de Wett, who gives himself away at the Old Manor and has to be fought.

In the books

In the short story “The Witcher” from The Last Wish, Ostrit is still alive and wants the striga left as she is. Her reign of terror makes Foltest look bad, and Ostrit hopes it will turn the people of Vizima toward Vizimir of Novigrad. On the night Geralt goes to the old palace to lift the curse, Ostrit offers him a bribe to leave the striga alone. Geralt refuses, Ostrit draws his sword, and the witcher knocks him out and ties him up. At midnight Geralt cuts him loose and uses him as bait. The striga finds Ostrit and kills him.