Dragons also appear as assistants to both Ûisang and Myôngnang . Ûisang in legend was aided and constantly protected by the dragon who had transformed from the Chinese woman , Shan － miao 善 妙 , while Myôngnang learned his mantic techniques from a dragon palace 龍宮 in China at the urging of the dragon king of the sea . Moreover , another text of sigillation belonging to the proto － Esoteric tradition , the Lung － shu wu － ming lun 龍 樹 五明論 , is attributed to Nâgârjuna . Just as in Ch ' oe Ch ' iwôn ' s tale of Ûisang ' s dream , the seal in this text is a “ diagram sutra of secret instruction by the bodhisattva Nâgârjuna " 龍 樹 菩薩 秘 決 圖經 formed of a square with sixteen “ gates " leading into it . It is thus possible that the “ blue － clothed youth " of Ûisang ' s dream was a figure from esoteric or mantic Buddhism , for one of the spirits of the five directions in the Kuan － ting ching , Ch ' an － che － a － cha wears blue clothes and dwells in the east . According to a late tradition in Japan , “ blue － clothes " equals Chin － kang tung － tzu 金 剛 童子 , who can be an incarnation of Amitayus or Ucchusma 穢 跡 金 剛 . He also wields potent seals .