Believe it or not, a eunuch can get it up and keep it up for a long time (read a book on the Ottoman sultan a long time ago) because no ejaculation.Retired eunuchs (I know...) sometimes married and their wives reported extreme satisfaction.A high price, however, for keeping Mama happy.
Different kinds of eunuchs. The episode hinted at that when Kalissi asked Missandie if she knew "how much was taken".Plus, as any married man can tell you, you can have a long marriage without having any sex at all.
Regardless if he's a dickless wonder, or not... Missandei's tongue, licking any part of the body, would be good to go!!!
I had to stop Anonymous comments due to spam. But I welcome all legitimate comments. Thanks.