Facemakers come from a long line of artists that can see inside a beast's soul. If they are good or evil, they can tell, The least experienced of them, know the techniques of the most experienced, but cannot do most of them. While the most experienced can just see off the bat if one is good or evil. . . the least experienced can at least tell when they are at least nearly finished their drawing of that beast. A Facemaker's job is quite difficult. They CAN draw what they see. . . but their drawing reflects the personality of the beast they are drawing.
The Facemakers concept came from the late, great Brian Jacques in his "Castaways" series.