In Greek mythology, the goddess of dreams and nightmares is Thanatos or, more specifically, Hypnos, who is often associated with the realm of sleep. While Hypnos embodies peaceful dreams, elements of nightmares can be linked to Morpheus, the god who shapes dreams. Together, they manipulate the dream state, influencing human experience and emotions during sleep. Their presence in mythology signifies the importance of dreams in understanding the subconscious and foreshadowing future events or emotional states, reinforcing the interconnectedness of reality and the dream world.