Andrzej Sapkowski, the author of The Witcher series of novels, is demanding more than $16 million in royalties from CD Projekt Red, makers of The Witcher series of video games. The demand was made public today online at a Polish stock exchange where shares of CD Projekt are traded on the open market.

The Witcher games are based on the novels which Sapkowski, who grew up in the city of Łódź, first published in 1986. Following its success localizing games for the Polish market, CD Projekt secured the license to create the first game in a new series, called simply The Witcher, which was published in 2007. The game was a success and catapulted its main character, Geralt of Rivia, into the global pantheon of fantasy heroes.

From our 2014 feature story:

According to CD Projekt Red, without The Witcher game, there wouldn’t even be The Witcher at all. The stories were popular in Poland, but the video game turned main character Geralt and his universe into a worldwide sensation. ”We weren’t buying The Witcher,” says [co-founder Marcin] Iwinski, referring to CDPR’s purchase of The Witcher rights from author Andrzej Sapkowski. “We were buying a [story] and then we turned it into The Witcher, which became known all around the world.”

An English version of Sapkowski’s letter, which we have embedded below, makes two serious allegations against CD Projekt. First, it claims that the royalty contract negotiated between the two parties runs afoul of a specific Polish law regarding royalty payments.

“It may be invoked when the compensation remitted to the author is too low given the benefits obtained in association with the use of that author’s work,” the letter, written by representatives for Sapkowski, states. “Notably, the latter condition is considered fulfilled if the compensation remitted to the author is too low by a factor of at least two.”

In an interview last year, Sapkowski revealed to Eurogamer that he sold the rights to the entire Witcher catalog to CD Projekt for a fixed sum, a decision he later came to regret.

“I was stupid enough to sell them rights to the whole bunch,” Sapkowski said at the time. “They offered me a percentage of their profits. I said, ‘No, there will be no profit at all — give me all my money right now! The whole amount.’ It was stupid. I was stupid enough to leave everything in their hands because I didn’t believe in their success. But who could foresee their success? I couldn’t.”

Rather than the lump sum payment negotiated previously, the letter requests six percent of the profits obtained for the lifetime of the franchise. For the earnings on The Witcher 3: Wild Hunt alone, the letter claims Sapkowski is entitled to at least 60 million Polish Zlotys, or around $16.11 million.

In addition to applying Polish law, the letter goes even further by claiming that the agreement between CD Projekt and Sapkowski only ever pertained to the first video game in the series.

“Therefore distribution of all other games,” the letter states, “including their expansions, add-ons etc., is, simply speaking, unlawful.”

In addition to posting the letter from Sapkowski, CD Projekt also posted its response. Roughly translated from Polish, it calls the author’s claims groundless.

“All liabilities payable by the Company in association therewith have been properly discharged,” it concludes.

Polygon has reached out to CD Projekt Red for comment.