Could someone give me a brief description of what exactly the Promethean race is? Are they Forerunners?
The actual Prometheans were basically Forerunner equivalent of Spartans. What we see in Halo 4 I assume are combat droids/robots that functioned as support or supplemental forces in large scale engagements.
Forerunner Prometheans (Organic): The highest warriors in the Forerunner military. Extremely large and powerful, they were deadly.
Promethean Defense AI (Mostly non-organic): These are the ones you encounter in Halo 4. They are defense AI, many different classes of them, that work together to defeat enemies. They were designed to combat the Flood, which is why the Knights disintegrate upon death and why their weapons disintegrate enemies.
Forerunner-built AIs, created specifically to combat the Flood and to defend Requiem from any possible hostiles. Carrying light-based weaponry and being unavailable to infection means they probably would have done quite a good job.
They could be semi-organic, and if this is the case they must have ridiculously long lifespans.
Defence AI on the planet Requiem.
> Forerunner Prometheans (Organic): The highest warriors in the Forerunner military. Extremely large and powerful, they were deadly.
>
> Promethean Defense AI (Mostly non-organic): These are the ones you encounter in Halo 4. They are defense AI, many different classes of them, that work together to defeat enemies. They were designed to combat the Flood, which is why the Knights disintegrate upon death and why their weapons disintegrate enemies.
JSA covered it pretty well… if you want more information the Forerunner cast system, I would recommend reading Cryptum by Greg Bear.