"Truth"

Grendel shows two different realities, shown by the Shaper and the dragon. Grendel first starts realizing the way the world really works, where beings are just present with no meaning. As he hears the Shaper, who "shapes" the way the people in the kingdom think, he knows that he is just creating a reality on the spot that he knows will be followed by anyone who listens. He describes a world of two different sides, the good and the evil, where Grendel, a monster (in the peoples' terms) fits right in the evil side. Grendel finds the melodic tones of the Shaper pleasing enough so that he would want to believe the things he says.
Th dragon shatters Grendel's hope to turn to a simpler, more ignorant reality, by describing blatantly how the universe works, including the complex scientific rules, and how the rituals of the people are just things organized by them, nothing with a higher meaning. Grendel eventually becomes angry because of the fact that the people are killing each other simply over beliefs that do not exist in the eyes of the dragon, and now him. So both the dragon and the Shaper are Shapers, but Grendel found the dragon's word to fit more with his perspective that following something made up, no matter how convincing, simply doesn't have any importance in life.