In Tower of Dawn, Kadja was a servant assigned to Chaol Westfall during his stay in the khagan's palace. Like most servants in the palace, she serviced her "masters" in any way they wished. She attempted to do this for Chaol when he first came to his rooms, requesting a bath. She prepared it but came out in a thin silk robe. He shut her down, saying he only wanted her to wash him and her only acting as a maid for the rest of the novel.
Throughout the novel, she was sent off on fool's errands by Yrene Towers in order to be kept from hearing what happened during Yrene and Chaol's healing sessions and reporting this to her unknown master. Yrene suspected she was a spy, as most of the servants were. She often brought them tea and honey afterwards but nothing else.
After Yrene had healed Duva, it was discovered that Kadja was in Sartaq's employ the entire time. She saw Duva leave to the tunnels and informed Sartaq and Nesryn.
Kadja was shown to be very docile but keen in the novel. She, like all other servants, is wary of the other royal siblings, such as Arghun since she didn't inform him at all of Duva's whereabouts.
She is described as young and fine-boned with thick, curly, chestnut hair that fell to her waist. She was also described as very beautiful, and often wore very sheer clothing.