In Greek mythology, the three-headed dog Cerberus serves as the guardian of the underworld. Representing the boundaries between life and death, Cerberus prevents the dead from escaping the underworld while allowing souls to enter. His fearsome appearance symbolizes the challenges of facing mortality and the inevitability of death. Cerberus's presence emphasizes the themes of afterlife and justice, reminding mortals of their choices in life and the consequences that follow. Thus, Cerberus plays a crucial role in mythological narratives regarding the cycle of existence.