Vessels are humans born containing powerful deities within them. Only awakening under certain conditions. There are six possible vessels, the the four compass deities (white tiger, azure dragon, black tortoise, vermillion bird ) and the yin and yang halves of the golden dragon. Usually there is only five as the two halves of the golden dragon cannot exist coherently. Though, on special occasions if the are born at the same moment they can exist at once. To awaken the yin half the vessel must meet the yang and have his/her soul realized. For the the yang the four compass deities mention above must assemble with the yang vessel. The human body cannot handle the powers of the four deities well and after awakening soon start falling ill. The vermillion bird vessel went blind and collapsed after hallucinating seeing Tatsuma . The white tiger's muscles started to have spasms. The azure dragon dragon began cough and seems to be sufficating. The tortoise have yet to shown affects. It is unknown if this also holds true for the golden dragon vessels.