The Witcher Season 2: 10 Monsters We Want To See
1. Vampires
If there is one concept in mythology that seems to be the most ubiquitous with every culture, it's the idea of a human-like creature that drinks the blood of its victims. You've got the Icelandic Draugr, the Greek Vrykolakas, the Japanese Nure-onna and many more. Therefore, it comes as no surprise that The Witcher features a large amount of lore regarding these blood-sucking monsters.
Part of what makes The Witcher's version of Vampires so great is that they exist as an entire subset of beasts, ranging in traits and skills. You have higher ranking vampires like Alps, Bruxas and Katakans that can appear human and have intelligence. But, you also have lower grades like Fleders and Ekimaras that are simply animalistic forces of nature.
This means that the series can have its cake and eat it too, exploring both monstrous/aggressive creatures and thoughtful/intelligent antagonists. Geralt's encounters with the beasts can range from pulse pounding battles to compelling character development.
Additionally, they are bound to make an appearance at some point, as there are some major characters in the books/games that belong to this species, with the most obvious example being Emiel Regis.