The main antagonist in Solo Leveling is known as the "Monarch of Shadows," also referred to as Ashborn. He is a powerful being who presents a formidable challenge to the protagonist, Sung Jin-Woo. The significance of the main antagonist lies in his role as a catalyst for Jin-Woo's growth and development as a Hunter. Throughout the story, the Monarch of Shadows pushes Jin-Woo to his limits, testing his abilities and determination. This antagonist serves as a pivotal figure in driving the plot forward and providing intense conflicts that showcase Jin-Woo's evolution as a character.