River Kings. Belying its monstrous size and appearance, the boiúna is a highly intelligent creature, even gregarious when properly approached by shamans or others performing the proper rites or seances. They occasionally don human guise, often appearing as wealthy nobles or merchants, and attend parties and dances as they mingle with mortal. Some keep a hordes of smaller snakes in and around their riverine homes in a serpentine semblance of the kingdoms they visit on land.