By surveying the background and the evaluation of the image of Vaisravana from India, China to Vietnam, by examining the historical and cultural background under the Pre-Le dynasty, associated with the image of Vaisravana, the article will help to explain the cause of appearing that strange dream and to clarify the contributions of Xen master Khuong Viet, not only the field of religious spirituality and also to the field of politics and military affairs for the cause of national building and defence in the late 10th century. In addition, by observing changes in the phenomenon of Vaisravana, the author also helps to recognise trends of forming and developing national consciousness in the process of history and regional relations.