Avenia is a country bordering Carthya, and an enemy of Carthya. It was ruled by King Vargan and was later ruled by Kippenger, a former Avenian Commander in The Shadow Throne. The capital of Avenia is Sparling, and other major cities include Isel and Dichell. The colors of Avenia are red and black, as mentioned in The Shadow Throne.
In the False Prince, it is mentioned that Avenia was on fragile terms with Carthya. Eckbert didn't want to anger any of the Avenians, as if there was a way, Gelyn would certainly ally themselves with Avenia.
In this, Avenian pirates and thieves have crossed the border of Carthya, stealing and even murdering the Carthyans. King Jaron, once again under the disguise of being Avenian, went to the pirates, wanting to know what they were doing.