Who is Head Black Eunuch from Persian Letters. Translated with an Introd. and Notes, by C. J. Betts and what is their importance?

The Head Black Eunuch is in charge of Usbek's seraglio while he is away in Europe. Kidnapped from Africa at the age of fifteen, he was castrated and put to work in a seraglio containing more than twenty women. Although he believes he knows how to properly control the women in Usbek's seraglio, he is not allowed to do so because of his master's kind heart. Before the eunuch can receive the permission from Usbek that he desires to take charge of the seraglio, he dies and another eunuch must be chosen to take his place.