Source: What Lies in Dust, pg(s). 88-89
Royal nagas are serpentine creatures that can be more than 14 feet long, with lustrous, jewel-like scales. However, the creatures can assume humanoid forms to deceive or interrogate intruders. 
Behavior & Ecology
These creatures are known to be exceptionally long-lived, exceeding 1,400 years of age in some cases. They can naturally cast arcane spells, and can blind or mute creatures with its hypnotic gaze.
Fascinated by history, they seek to dominate the most notable sites of ancient ruins, seeking to drive away all rivals. Although dark nagas and guardian nagas have a deep respect for the them, royal nagas and spirit nagas are virulent enemies.