Detecting demons was precisely one of the capabilities that Wang Chen had stimulated and mastered with the spearhead of the Taichu Slaying Demon Spear.
Wang Chen had once tested it with the head of a Bloodthirsty Demon; as long as he kept the spearhead close to his body, he could sense the presence of demonic aura within a certain distance.
Humans have Qi, demons have demonic auras, and the principle of the Demon Identifying Talisman originates from this concept. However, some demons are extremely adept at concealing their auras, and these Daoist talismans are not infallible.
But as long as a demon exists in this world, even if it devours souls and possesses bodies, it cannot completely hide its demonic aura.
Wang Chen had also conducted tests on the demons imprisoned in the Prefecture Guard's dungeon and confirmed the merits of the Demon-Slaying Spear's head. Therefore, he had always carried it close to his body, integrating it with his heart.