• What exactly is a soul, and what happens to it when you die or have it removed.
• Are "Blanks" and "Pariahs" the same thing, if so would that not make the soulless Necrons impossible for the Eldar to fight?
• If the C'tan are completely physical beings why do they eat souls?

So after some pretty extensive reading, it seems a soul is both the life energy of a being and it's connection to the warp.

Warp wasn't always "the warp". It was originally the realm of souls quite literally. Then, suddenly, Chaos.

Actually the eldar are VERY good at fighting the necrons precisely because the necros have no connection to the warp and thus without significant hijinks in place, no warp defence so to speak of, the eldar where made to roll around the galaxy eldrich storming the 'crons to death after all.

Some eldar pariahs also do exist but they are stupidly rare and in the massively psychic eldar society are even more outcast, but hey, they have one option available to them and thats go work for the black library handling the universe largest collection of knowledge on chaos.