Cestimir was a Rshani prince, the son of Nadiushka and Lankomir. In his childhood he was tutored by Alexyin, a former Setna who had once instructed his older half-brothers, Nadei and Nazheradei.

Cestimir grew up in a strict household and strove to honor his mother wishes and live up to the duty his high birth had placed upon him. He was a gifted and serious student, sullen and mischievous by turns, with a disturbing habit of saying exactly what he was thinking. He was acquainted with two of his half-brothers (Vladei and Eleferi), but knew from an early age that they were better viewed as deadly rivals rather than kin. With prince Nadei dead and Liall exiled, Vladei and Eleferi were the only other possible claimants to the throne.

Cestimir loved to race his sleigh outside the palace grounds with his driver, the fierce Yesuk, but found few opportunities to escape his responsibilities. He was very fond of Lady Ressilka, whom he hoped to marry. He once asked Liall if he found her pretty.

Vladei believed that Naduishka's policies of an open trade market and relaxed borders were dangerous. He believed that Cestimir shared his mother's political views - which Vladei opposed - and that removing Cestimir would make him king. Aided by Melev the Ancient, Vladei sabotaged Cestmir's sleigh, causing it to crash. Yesuk was killed and Vladei and his guards waylaid Scarlet and Cestimir as they tried to make their way back to the Nauhinir. They were taken to the ruins of Temple Road. Melev spirited Scarlet deep into the ruins while Vladei killed Cestimir, decapitating him with a sword.