The author uses Grendel's words and Grendel's thoughts in the excerpt to develop Grendel's character. These reveal his personal perspective, motivations, and feelings directly, providing insight into his nature and inner conflicts. Hrothgar's words and perspective are not used to develop Grendel's character in this context. This approach allows readers to understand Grendel beyond just how others see him, by focusing on his own expressions and reflections.