Good question about the Messengers. I would say that they are taken/kidnapped from childhood and 'programmed' by priests and trainers, indoctrinated into the ways of the Unlife at an early age, and made into essentially sociopathic killing machines. They come from all over; it is likely that they are not assigned to the exact same area as they were taken from, because there should be no chance of them meeting family later in life.
Another way to go would be that there is a group of priests that go out searching for the few individual youngsters who have a "special quality" that would make them a great candidate for becoming a Messenger. This special quality could (should) be the fact that they are naturally born sociopaths. For only one who truly does not care about anyone or anything could dedicate their life to the destruction of all life. This could be used in a story about trying to save a child from the priests - before indoctrination - only to have that child kill someone (a sibling, parent, "friend", etc...) after being returned home. This could bring up all manner of drama/conflict for the PCs, particularly if they are heroic and not just mercenary.
This is a welcome addition to my RM/SW collection and I cannot wait until I can get it in physical form (nothing like holding the book in your hand, I believe). I also agree that the size is not a problem, I like more/bigger so getting "blown up" was only a good thing.
My only complaint is the cultural/architectural style presented (and to a lesser degree, the way magic is said to be perceived by the people of the world, but that has been hashed* out on the message boards to death). To me Kulthea is a High Fantasy setting, not some Middle-Ages Europe with magic and monsters as so many settings are, such as Greyhawk and The Forgotten Realms. This means, architecturally it should be more like ancient Mesopotamia and Assyria, with the added element of being a magical world, as well as one filled with dangerous creatures, some of which fly. (A great example is the city-state of Tyr, seen here:
http://s1230.photobucket.com/user/zedecksiew/media/tyr1.jpg.html, though not everywhere is hot and dry, so some extrapolation for the more temperate and cold climates would be needed. Another great example, from one of your own products is the Dragonlord Citadel in NE Jaiman; that place was/is awesome.)
So please, can we get more of that into the art (& maps & description & character images) and less of the typical fantasy stuff that is out there now.
*OK, to be completely fair, so has the problem I am bringing up here, but I just felt
I needed to restate it.