With massive red robes it would work, but only because no imperial knows what a Necron is yet - throw Eldar shaped spanner in works and you could have a fun little story
How would that even work? Don't most Tech-priests have some flesh left? Could he mimic Mechanicum tech?
Perhaps he could first appear disguised as a Cult Mechanicum Techpriest?
Or he could simply do as most Necron Lords do in such situations, appear via proxy through the use of Mindshackle Scarabs, no need to disguise yourself as a Cognoggin when you can simply hotwire one and go for a ride. He can then drop hints in conversation as to his true identity that someone in-universe would be oblivious too but an omnipotent reader like ourselves would understand, perhaps mentioning a collection, the lights on his augments momentarily flickering an eerie green, etc, whatever's appropriate for the situation.
Edited by SanguiniusReborn, 05 December 2018 - 12:23 PM.