Certes is a Kingdom in the north-east of Imperia. The people believe in a single God. The Kingdom was one of the three Kingdoms which declared war on the other countries of Imperia, Athos and Thena being the other two. Certes' army is feared for their fearlessness.
There is a Certan carpet which can be bought from Mavda, implying that even though no one could cross the borders of Elyria, she somehow manages to import some wares from Certes. You can also purchase the Certan tome from her, further proving this theory. Elena's father was saved during the war by a Certan, even though they were on opposing sides.