The Dauk were members of a possibly human culture about which not a lot is known. Eltibald studied their menhirs in his investigations into the curse of the Black Sun.
Eltibald wasn't mad at all. He deciphered the writing on Dauk menhirs, on tombstones in the Wozgor necropolises, and examined the legends and traditions of weretots. All of them spoke of the eclipse in no uncertain terms. The Black Sun was to announce the imminent return of Lilit, still honoured in the east under the name of Niya, and the extermination of the human race. Lilit's path was to be prepared by "sixty women wearing gold crowns, who would fill the river valleys with blood".
The surviving writings found on the Dauk menhirs and tombstones found in Wozgor necropolises formed the basis of several prophecies and divinations (vide: "The Prophecy of the Black Sun"), which remain questionable to this day (vide: "The Mania of Mad Eltibald"). Some scholars stipulate that the Wozgor and Dauk beliefs remain alive in the form of the religion of Melitele and lesser cults (cf. Coram Agh Tera and Veyopatis). The events which led to the extinction of both peoples remain sharply disputed among scholars."
Annanias Uldvikel, "Ancient Human Cultures and Their Relicts"
Yarra: the River of Death, a scenario for The Eye of Yrrhedes role-playing game, mentions a tribe called dauk-vorkers belonging to a race called vorkers, who were described as 1.20 meters high, stocky humanoids with Mongoloid facial features, somehow similar to goblins by customs and behaviour. Another tribe mentioned were halla-vorkers.
It should be noted however that the scenarios are set in the world different to the one described in The Witcher novels.