Gregor is the protagonist of the Underland Chronicles. At 11 years old, he is determined to find his father and bring him back home to his mother and sister in New York City. Fiercely protective of his younger sister Boots, Gregor denies at first that he is the warrior from the Mysterious Prophecy of Gray. However, over the course of the novel, Gregor shows great resourcefulness and ultimately embodies the Warrior Archetype without needing to raise a sword or cause destruction. Gregor becomes a warrior for peace.

Gregor also develops as a character who trusts those around him. At first, he flees the Underland humans, only to discover they’re his friends. He doesn’t trust the bats with Boots at first, but later trusts them with his own life in the canyon. He wonders whether to trust Ripred, but he risks bodily harm to protect him from Henry. By the end of the novel, Gregor is confident in his allies and is more confident in himself—he decides he doesn’t even need a sword despite the dangers he’s faced.