Naja is a genus of venomous elapid snakes known as cobras. Several other genera include species commonly called cobras, but members of the genus Naja are the most widespread and the most widely recognized as "true" cobras.
... That means that many different versions are required because there are so many poisonous snakes are found throughout the world - Cobras, mambas, kraits, vipers and pit vipers, to name just a few...