"The Emperor checked the ornate bolter at His hip. One of the very first boltguns; a progenitor for its kind – not a relic rediscovered from the Dark Age of Technology but an invention of the Emperor’s own design."

This is memories of custodes Sagittarus about the times of Unification Wars on Terra from the book "The Master of Mankind"

This is the thing I wanted to show you. One of the very first boltguns made by the Emperor himself.

Actually, I didn't want to show some historical event from the Emperor's life. This is something like a symbolic composition(?)

The Emperor lights His way through the Galaxy with the flame of His Sword, behind Him is Holy Terra, which frames His head like the saints halo, and beneath Him are the bones and sculls of those who perished in the endless war that He unleashed.