Part guardian, brother and companion, the bloodriders guard and accompany the khal in his daily routine. They share what is his, sometimes even his wives, but never his horse. Sometimes a bloodrider may also be a ko, one of the leaders in charge of the khalasar's component parts. The bloodriders and their khal refer to each other as "blood of my blood".
Only a khal can ask a man to become his bloodrider, by saying "I ask your oath, that will live and die as blood of my blood, riding at my side to keep me safe from harm."
Ancient traditions proclaim that when a khal dies, his bloodriders die with him. Should the khal die in battle, the bloodriders live only long enough to avenge him. Once done, the last service the bloodriders must perform is to escort the khaleesi to Vaes Dothrak to join the dosh khaleen, and then they are to join their khal in death.
A Game of Thrones
Traditionally only a khal may have bloodriders. After the deaths of Khal Drogo and Rhaego and the disintegration of Drogo's khalasar, Daenerys Targaryen asks Aggo, Jhogo, and Rakharo to be her bloodriders, asking for their oaths, using the same words that a khal would. At first all three refuse, but after witnessing the extraordinary birth of her three dragons they swear allegiance to her, declaring her "blood of my blood" just before Daenerys rises amidst the ashes cradling her three newly-hatched dragons.
- to Jhaqo
—thoughts of Daenerys Targaryen