system
Given the following post, respond as if you're commenting on Reddit:
human
[Wh40k] about the nature of the necrons...

Are they ACTUALLY robots (biological creature's mind downloaded into a robit body like a file) , or are they more like Al from FMA? (Soul bonded to an object that is used like a puppet)
gpt
The former. 

Depending on the quality of the body (Warriors being the lowest junk, Lichguard and Overlords being the best) the mind of a living being was converted into stored and simulated data with varying amounts of success. In the lowest cases, it offered no more than a basic set of motor skills and recognition of station. In the highest cases, the entire concious mind, complete with memories, was converted.

The Necrons sacrificed their souls in the conversion, however. No Necron has any warp-connection, nor any lingering presence of the spiritual link that would be called a Soul. They are entirely artificial (though i wouldn't say digital, as the Necron tech goes well beyond that).