The Faceless, an Alpha Legion Warband, operate in the Ultima Segmentum. They are notorious for using subterfuge and misdirection to outsmart their enemies.

The Faceless take this approach to the extreme by undergoing cosmetic surgery to make their faces identical, equipping the same armor, and taking the name Alpharius, even in the presence of other Alpha Legion Warbands. This makes it impossible to identify their command structure and causes confusion on the battlefield. You may never know how many Alpha Legion members are involved in an operation.

My warband applies the concept of the Faceless to the tabletop. So members use the same armour, specifically Mk.VI armour from the plastic Horus Heresy kit. I customised the helmet in Blender to emulate the Headhunter kit from Forgeworld. And added cameleoline cloaks using foil from a takeaway dish and Mulliput.

On the tabletop, people usually celebrate having many customised and unique characters in an army, especially in Warhammer 40,000 where heroes are rife.

An army of Chaos Space Marines where all members are identical is an interesting concept and fits narratively with the Alpha Legions secrecy in the lore. Chop off the head of the Hydra and two more will take its place. So the leader you thought slain may, in fact, be a distraction.