A ko is a commander within a khalasar of the Dothraki. He can be protected by a khas. If a khal dies without a strong successor, his kos might fight amongst themselves and form their own khalasars.
A Game of Thrones
- Aggo, ko to Daenerys Targaryen
- Cohollo, ko to Drogo
- Jhaqo, ko to Drogo
- Jhogo, ko to Daenerys
- Pono, ko to Drogo
- Rakharo, ko to Daenerys
Daenerys: I name you ko, and ask your oath, that you should live and die as blood of my blood, riding at my side to keep me safe from harm.
Aggo: I cannot say these words. Only a man can lead a khalasar or name a ko.
Daenerys: Why should I fear Pono? He was Drogo's ko, and always spoke me gently.
Jorah: Ko Pono spoke you gently. Khal Pono will kill you. He was the first to abandon Drogo. Ten thousand warriors went with him. You have a hundred.