Eygor was ”a squat, hunched Human man with sallow skin, awful posture, bushy black brows, and two large, oddly protuberant eyes.“ In 1974, he was part of the Chrysalis Project, in charge of babysitting the children of the Developmental Deviations Unit. (TOS novel: The Rise and Fall of Khan Noonien Singh, Volume 1)
It is implied that he is the same Eygor as the character from Young Frankenstein.