Ornon is Eddis's ambassador to Attolia. After the treaty was signed between Eddis and Attolia, the ambassador was given certain authorities superior to the queen's. He and Eugenides are described as old nemeses for being at odds, though with a grudging respect for the other, though Eugenides never explicitly mentions why Ornon came to respect him.
In The Queen of Attolia, Ornon is the emissary who deliberately tries to anger the Queen of Attolia into killing Eugenides after she captured him so that he would be "safely dead". Though Eugenides does not witness the act, he grudgingly comes to respect Ornon as a result, knowing that Ornon understood the importance of Eugenides's willingness to sacrifice his life for Eddis.
Ornon plays a fairly important role as the assumed head of Eddisian-Attolian relations and an important advisor to the king in the third book of the series. Like many others, he is frustrated by Eugenides's reluctance to act as a king, though he is not reckless enough to openly force him to act as such. However, given the king's mercurial temperament, he does not hesitate to force Eugenides into submission if the king endangers himself needlessly. Ornon is a capable diplomat, though he occasionally dispenses his political authority for more trivial reasons, such as telling Costis is told to keep the king in his bed due to the fact that Costis "is dispensable, politically speaking," should he fail in his task.
Eugenides and Ornon have some history involving Ornon's sheep that is hinted at through The King of Attolia, but never really explained. In the past, Ornon had apparently been very wealthy and owned a great deal of sheep; however, undisclosed circumstances resulted in the loss of all the sheep, possibly due to Eugenides.
Eugenides can infuriate Ornon by making sheep noises, and one of his cousins makes a reference to being "As rich as Ornon before he lost all his sheep."