"I do not believe it diminishes them," Harrow says carefully, aware she is out of her depth slightly. "Over time, spirits in the River become less stable and able to interact with the living world, I know, and I do not believe it protects them from this entirely. For that reason they cannot serve indefinitely. But I have not heard it makes matters worse."

"If they were tempted to change or hide a message--or even desert--I suppose they could, just as a mortal messenger could. I imagine the risk would be greater if we were at war with other necromancers, who might be able to intercept and bribe or coerce our messengers."