Rp secnario one: people screamed in pain and terror as a entire being of a ork Waaagh assaulted the planet only a few Astartes to help as almost the entire ssector fleet was busy fighting a massive chaos fleet aswell with most forces leaving other planets like this defenseless and now you and whatever batch of left behind guardsman or others fight a wasagh and most unlikely for you on this front the big boss HER self appeared
(sorry I had too when I saw this image)