Who, or what, is Dr. Narud? (Spoilers)

I am not well versed in Starcraft Lore outside the campaigns of the 4 existing games, so I was quite surprised that the mild-mannered Dr. Narud of the Möbius Corporation from Wings of Liberty was actually a shapeshifter / psionic entity intent on destroying the zerg in Heart of the Swarm.

It has further come to light that "Narud" is simply "Duran" backwards -- is this a nod to the infested terran Samir Duran from Brood War? Is it the same being?

Can anyone shed some light into who, or what, the good doctor truly is?