The Witcher: The Catriona Plague Explained (Did Ciri Really Cause It?)

Many people may not know this, but the multiverse is very present within the "Witcher" setting. While Netflix could lean into this concept to explain how Geralt transforms from Henry Cavill into Liam Hemsworth, it wouldn't be the first time another universe affected the Continent. That's because Ciri more or less brought the Bubonic plague into the world of "The Witcher" via her multiversal travels.

The Catriona plague is a disease that quickly spread through the Northern Kingdoms after Nilfgaard's invasion. According to the glossary in "The Witcher" video game, "Those who suffer from catriona die a terrible death – their convulsions become stronger each day, they vomit blood and mucus, and have bloody diarrhea. After a fortnight or so they die in agony."

As for how the Catriona plague arrived in the Northern Kingdoms, all eyes turn to Ciri. As the young princess traveled through space and time, the novel "The Lady of the Lake" implies she landed in medieval Europe during the Black Death. She wasn't there long, as the corpses in the streets horrified her, forcing her to quickly jump to another point in the time-space continuum. Unfortunately, she was there long enough for a few fleas to latch onto her, and as she returned to Nilfgaard, the insects found a sewer rat to call home. The rat then boarded Catriona, a ship headed for Cintra, leading the disease, known as the Red Death, into the Northern Kingdoms.

As a distant descendant of Lara Dorren, Ciri has Elder Blood running through her veins, coming from an ancient mixture of elvish and human blood. Elder Blood gives Ciri powerful magic, allowing her to do incredible things like visiting different worlds. However, it also puts her in the middle of a dooming prophecy, regardless of which version of "The Witcher" you're experiencing.

From an early age, "The Witcher" ties Ciri's fate to Ithlinne's Prophecy, but what exactly that means depends. In the books, the prophecy states that someone of Elder Blood will usher in a new world following the destruction of the current. For the on-screen universe, Netflix altered the wording of Ithlinne's Prophecy, with "The Witcher: Blood Origin" implying that an individual with Elder Blood will be involved with the world's destruction, making Ciri's destiny much more bleak. Either way, it's clear why so many parties want to get their hands on Ciri and her magic.

Although the disease has yet to play a factor in the Netflix series, the Catriona plague is an excellent example of how powerful Ciri could be. In the book, she makes a simple mistake by letting some fleas latch onto her, and it subsequently causes the Red Death, showing how powerful she is even when she isn't trying. Imagine what someone with her potential could accomplish if they devoted themselves to a certain task. Unfortunately, the people of the Continent have realized the latent potential in Ciri's magic, forcing her into a lifetime of running in all adaptations of "The Witcher."