What about kikimora, drowner, noonwraith and koshchey? For that matter, virtually every monster has its analog in the mythology of Western Europe. The thing is, the game developers are Polish, the author of the book is Polish, so why not take the chance to popularize the Slavic folklore? I want the foreigners to become acquainted with our common Slavic mythology.
For instance, in the game a poludnica is called a noonwraith. A western player might have a hard time trying to found out more about the monster's origin, its mythological prototype.
The Witcher books are not Slavic mythology, but instead they are heavily influenced by Slavic mythology. It is important to note that Sapkowski was inspired by other mythologies as well, although Slavic remains the most influential nonetheless.
For example there is a legendary white haired monster hunter and warrior in ancient Persian mythology called Zal
http://en.wikipedia.org/wiki/Zal. Zal's story is part of the Shahnameh
http://en.wikipedia.org/wiki/Shahnameh, which is a collection of Persian mythology written by Ferdowsi more than 1000 years ago. Zal and Geralt share some notable characteristics such as the iconic white hair and monster hunting. Simurgh
http://en.wikipedia.org/wiki/Roc_(mythology) is an ancient monster in the Persian mythology, and its name was abbreviated to Roc by Louis Charles Casartelli. Roc
http://witcher.wikia.com/wiki/Roc is also present in the Witcher universe, and the abbreviated version of the name is used and not the original Persian name. The Griffin present in the Witcher originated from the Persian mythology as well, and it is called Huma
http://en.wikipedia.org/wiki/Huma_bird in Persian. Yet we all know it as the Griffin. Griffin is also present in Greek and Egyptian art and lore, but it is known by different names in those cultures.
So it is a common practice to translate or abbreviate monsters' names across different cultures.
I personally love Slavic, Persian, Greek, and Egyptian mythologies, and I also enjoy ancient beliefs and stories of the Aztecs and Mayans. But I believe it is wrong to try to shove cultural material down players' throats if they are not interested, because it is going to have adverse effects. If they are interested, then they'll do research and learn about it themselves. There are better resources than a video-game for that.
I get your enthusiasm though, because I am a HUGE mythology fan myself