The painting depicts Zhongkui (鍾馗), a fierce deity in Chinese mythology who exorcises evil spirits. His image is displayed in homes and businesses for protection.
It's said that Zhongkui gained top honors in the imperial examinations, but the emperor denied him the title of Zhuangyuan (top scorer), due to his appearance. In a suicidal rage, Zhongkui hurled himself against the palace gates, crushing his skull and dying on the steps.
Penalising Zhongkui's grievance against the emperor, but seeing great potential nonetheless, underworld judge Yanluo Wang tasked Zhongkui with hunting, capturing and maintaining order among ghosts. With diligence and success, Zhongkui soon became 'King of Ghosts'.
Zhongkui is depicted in art with up to five flying bats, being the five fortunes (Wufu) of health, wealth, long life, love of virtue and peaceful death. ('Bat' and 'fortune' have the same pronunciation in Chinese.)