|No one can have everything. Nobody is being born a sorcerer. And none should be born as one! After all, all the students should decide for themselves whether they want to be sorceresses or mothers. I demand all the students to be sterilized. No exceptions.|
|- Tissaia de Vries, The Poisoned Source|
Tissaia de Vries (d. 1267) was a sorceress and a member of the Chapter of the Gift and the Art. She was one of the rectors at Aretuza and the author of The Poisoned Source. She was also extremely obsessive about her appearance and things in general. Tissaia was the one who took a young Yennefer of Vengerberg under her wing. It was she who fixed Yennefer's hunchback and cured her of her various afflictions. During the coup on Thanedd Island, it was she who teleported a heavily wounded Geralt and Triss away from the hands of the approaching Redanian army. After the coup on Thanedd Island, Tissaia committed suicide slitting her wrists. Together with the other losses, her death spelled the end of the Council, making way for the Lodge of Sorceresses.
- De Vries is a common Dutch surname meaning "the Frisian".
- Vries can also mean "freeze".
- In Andrzej Sapkowski's Dynastic Descriptions, it's mentioned that a young Ilona Laux-Antille was Tissaia's assistant at one point.
- In The Witcher, there's a potion called De Vries' Extract.
- In the first game, there's an in-game book, Sorceresses and Sorcerers, that mentions her.
- In The Witcher 2: Assassins of Kings, she's mentioned by Geralt as a co-author of the compendium Masters of Magic on Curses – Selected Writings, with Margarita Laux-Antille.