Find a local man, Borr Iskoph( 458, 19, -449 ) , at a small campfire past Agent Zhatia at the Iksar Hero statue's ledge. He will mistake you for his Rime contact and, when he realizes his mistake, he attacks.
Collect the letter on the ground.
Take the letter to Zixka
When he realizes his error, he says, "Ulkorruuk help me! You are not my contact!" Ulkorruuk is the Lady of Betrayal, a Demi-Goddess of the Plane of Hate.