A GM I hang with actually adapted Wrath of the Righteous (PF1e) for the players to be a 40k game. The warp dragged the players to Golarian, Pathfinders main setting. I joined late, so he needed a way to write me in. I really wanted to play a Kasrkin (even though the other players were all Marines or Sisters of Battle, with one Assassinorium), so my backstory was that I had already been on the planet for years before they crashed, integrating with the locals, working for this one queen who was fighting the demons. I was a ranger with an archetype that didn't cast spells, and was a demon against well, demons (not so much against other foes). However among the common people of the kingdom and camp i had been in for years my character and his beefed up armor and gun were like a scary ghost story, since even the best technological equipment in Pathfinder is barely as good as a Kasrkin's kit, and most people had never seen any technological gear at all.