In Beowulf, Grendel is a very static, one dimensional character with only the most base and inhumane characteristics. He is written as a mindless beast, motivated only by the desire to consume human flesh and bring Hrothgar's kingdom into darkness. John Gardner adds a totally new perspective to Grendel, particularly with regard to Grendel's attitude toward people and society. In Beowulf, Grendel's only interaction with humans comes when he goes on raids and attacks them. His determination to kill every human he comes in contact with seems to be fueled by a senseless, animalistic passion, and renders him as a being incapable of rational thought. Gardner attempts to change this characterization, as he portrays Grendel as something like a confused adolescent trying to come to grips with his place in the world. I think the biggest changes Gardner makes to Grendel's character are the basis of his origins and his introduction to Hrothgar's kingdom.
Early in Gardner's novel, Grendel is deeply frustrated with what he deems to be an over-mechanization of the world. He views the animals, the weather, and even his illiterate mother, as non thinking beings. He feels completely alone in the world, especially with his mother being unable to communicate with him. Grendel even begins to question whether or not he exists himself. This frustration leads him to wander into the woods, and exploring the outside world like he never has. He gets himself stuck in a tree and is charged at repeatedly by a bull. He eventually passes out and is awakened by a younger Hrothgar and a group of Danish warriors. Grendel can understand their words, but they are unable to understand him and begin attacking him. Had it not been for his mother's swift rescue, Grendel would have been killed. Despite their unprovoked aggression towards him, Grendel speaks of Hrothgar with great admiration, saying, "He reshapes the world...He stares strange-eyed at the mindless world and turns dry sticks into gold." This shows his deep desire to take part in civil society, and the fact that he is unable to comes through no fault of his own.
In Beowulf, Grendel is described as being a descendent of Cain's clan. This designation makes him an outcast not only from society, but from God himself; making him more than simply a monster or a beast, but an instrument of evil, the living embodiment of Satan. In the novel, we find out that there is no proof for this claim, and that Grendel only believes it because he misinterprets Shaper's telling of the story of Cain and Abel, which he indicates by saying, "He told of an ancient feud between two brothers which split all the world between darkness and light. And I, Grendel, was the dark side, he said in effect. The terrible race God cursed."At this point Grendel is desperately searching for an identity, and since the humans have cast him aside as a freak, he decides that he would rather play a fictional role as their scourge than as a pitiful outsider. This change in Grendel's back story transforms Grendel from a beast destined to wreak havoc on man to a confused young being who is simply trying to find his place in the world.
When Beowulf was originally written, Grendel's character seems to represent the dangers of the outside world, and the necessity for unity amongst kingdoms. However, with Gardner's novel in the mix, Grendel's character takes on a fully new meaning. Rather than signaling a need for strength, Grendel signifies a need for compassion and understanding. Had Hrothgar and his men shown the slightest amount of consideration, they would have found an extraordinarily powerful ally in Grendel. However, their rush to demonize and antagonize him leads to a bloody conflict. Since Gardner wrote this novel in 1971, we might be able to make the hypothesis that he was attempting to send a different message. Using the context of the time period, we might say that he was comparing Grendel's fight for recognition to that of women and minorities struggle for equal rights. Like Grendel, both these groups were attacked unfairly as they struggled for recognition, and nasty conflict occurred as a result. Whatever Gardner's intentions, his novel revolutionizes our outlook on Grendel, and transforms him from a one dimensional beast to a sympathetic, misunderstood child.