After thinking I will play a nation surrounding the Caspian Sea and extending to the Black Sea. Pretty much it would control the Caucasus to the Caspian Sea or a s they call Hyrcania.

Also very good historical map for the period. I suggest you put it on the OP.

http://www.worldhistorymaps.info/images/East-Hem_476ad.jpg

Edit: NVM. I will RP instead as the Sassanids except larger.