Ear of Thrane: Spy
Use the Spy background, with the following additions.
During the Last War, you were an Ear of Thrane, acting as a spy for that nation, pretending to be a loyal soldier for a different nation. When the war ended, your secret identity was learned. Untrusted by your former friends, you found that the nation of Thrane also mistrusted you, thinking you may have been a double agent. Mistrusted now by both sides, you are a spy without a home.