Truth

The Shaper sings songs of the "truth", glorified battles, events, glossing over humanity and Hrothgar's victories. This enraptures the soldiers and subjects to remember only what they want to remember. Not the bloodshed, not the violence, or the death, just the victory, the bravery, and the triumph. In general, those memories are much more preferred to a human, and so the Shaper takes advantage of that, by using his artistic abilities. Grendel, however, fully knows how gruesome and violent and evil humans can be. What one human would do to another, how close to monsters they are themselves. But, he, too, also wants to believe in the sweet null and veneer the Shaper casts. What the Shaper provides is part of the truth, however, without the whole truth, it is just a lie.
Someone once told me that they received an A in a very difficult class. The fact that they have an A is true, however what they left out was that they cheated in order to get that A. Part of the truth just doesn't cut it, that A means something different once I found out that that person cheated.