Najády are one kind of nymfa, which is to say that they are members of a large class of female mythological entities in human form. In particular, they are associated with water.
Ve hře Zaklínač
Najáda is a nymfa who enjoys the waters of the eastern shore of the Bahnice and the river near Víska Bahnice, where she delights in the presence of Paní. However, utopenci have lately been harassing her, most likely under their leader, Zefír's orders, to the point of stealing her náhrdelník s tyrkysem, a gift from Paní jezera.
She is also a skilled healer and as one possible reward for services rendered, she grants the witcher the status of lifelong patient.
see her censored full shot here