Complex sentence: The white sends Karris to the Tyrean capital of Garristos to spy on its satrap's army, with a note informing her of Gavin's unfaithfulness, instructing her to not read it until after she leaves the Chromeria.
Split into simpler sentences: The white sends Karris to Garristos, Tyrea's capital, to spy on its satrap's army. She gives her a note informing her of Gavin's unfaithfulness, instructing her to not read it until after leaving the Chromeria.