Messengers were employed by local aristocrats and religious dignitaries who, as their name implies, deliver messages. Depending on the campaign, magic or technology may have taken up some of the messenger’s work load, but there will always be people who lack the means to send magical missives or who avoid using magic out of a desire to remain undetected.
In any event, messengers were a critical to the function of Medieval government and religious institutions. They needed to be highly motivated, brave and self-reliant people, as the journeys they undertook sometimes brought them through dangerous terrain or into the hunting grounds of predatory animals, such as wolves. And, of course, they often had to bring unpleasant news to powerful people. The common phrase about “killing the messenger” represented a real danger for historical messengers; in fact, laws were eventually enacted to protect messengers from the fury of angry message recipients.
In a Dungeons & Dragons campaign, messengers can be reliable sources of information about the condition of roads and river crossings, troop movements, human or humanoid banditry and happenings in nearby settlements. If the heroes discover the remains of a slain messenger, several adventure opportunities can emerge, depending on the contents of the message. Delivering an unopened message to its intended recipient will likely bring an ally to the heroes’ cause, but opened messages – particularly correspondence between villains – will probably draw your heroes into adventure very quickly.