Assassin -- or whatever was now within his body, which had been severely deformed, much of it only skeleton, other parts rotting away, some of it filled now only with dark energy -- appeared on the planet. He was... Hungry. So many lost spirits here, wandering to the afterlife. So many remains, nothing but dust, covering the planet.
And Assassin began to devour. His mouth opened wide, his teeth like a monster's, cutting through both the Physical and Astral Planes as he literally... Began to devour spirits in the Astral Plane and spirit energy in the Physical Plane. He was devouring dead Narrikians.
And with each bite, his body grew... Darker.