The Arcanum is the Moth Kinden's secret service. That said, it is not a single, overarching organisation. Individual Skryres or groups of like-minded Skryres sponsor agents and may or may not share their findings with their peers, depending on a number of political issues. This does not mean that they are in any way less competent, however. Arcanum agents are found all over the Lowlands, and even into the Empire. It was Arcanum agents that arranged for the 'occupation' of Tharn to be much milder than normal, and on the Moths terms.