Eunuchs

Eunuchs are men who have had some or all of their sexual organs removed in order to make them more efficient servants, as they are not distracted by lust or sexual matters. The practice is considered cruel in Westeros, where eunuchs are mistrusted, but is considered acceptable in many parts of Essos.

Season 1
Grand Maester Pycelle expresses distrust of and disgust with Varys, and is annoyed that a eunuch is serving on the king's small council.

Petyr Baelish talks to Varys about his disfigurement as part of a verbal sparring match, asking where his testicles are located. He notes that Varys is from the Free Cities.

Season 3
Daenerys Targaryen travels to the slaver city of Astapor to hire an army of Unsullied, slave soldiers who have been turned into eunuchs to improve discipline. Lacking sexual urges, they do not take part in rapes or sackings of captured cities, and are noted for their unquenchable loyalty to their employer.

Known eunuch characters

 * Varys, the Master of Whisperers on the small council in King's Landing.
 * Grey Worm, commanding officer of the Unsullied forces hired by Daenerys Targaryen.