Moiraine

"And one might presume," she concludes, "that for the type of person who would swear such an oath, it would in most cases be kept."

In most cases, save for those of intentional treachery, spying, and deception, of course, should the dead be able to main such will.

There is one way to learn more, of course.

"... do the messengers retain their free will, or become -- lesser, somehow?"