I enjoy coming up with ideas plots set in 40k, not that any of them really ever go anywhere, and I enjoy making them interesting. One thing I like to do is create unlikely alliances/team-ups. But I don't want them to go against established fluff and what not. So basically I think I'm asking is that is: What are some cool team-ups or alliances that I could use as inspiration? These wouldn't necessarily be permanent set ups. I see most of them as matters of necessity. Like Space Marines and Chaos teaming up against Tyranids. (first thing that sprang to mind) but turning on each other once the threat is resolved.