I was certain I read it somewhere, and would be fun if the Dark Angels suck that bad at security.
I think I read that too, but DA security's great, they infrequently have a chaplin wander past and check through the window to make sure he's still babbling and insane in the corner of his room. But to make sure there are no security breaches, about twenty Dark Angels know he's there at any one time. So, minimal security, no one would recognise him if he escaped and they are leaving a mentaly unstable genetically engineered super human who tried to kill their primarch chill out next door to said primarch whilst he's taking a nice nap.
Slightly off point, but wouldn't all the primarchs in stasis or who wandered off into nowhere land get the surprise of their lives when they woke up/got home. I mean for starters, the emperor's definately a god now, but he's also dead, so be careful around that touchy subject. We've been doing OK without you, as Matt Ward made sure that a couple of Grey Knights (we'll fill you in later) easily outstrip any of your feats without breaking sweat. Psykers are OK now, but we still have dudes wandering around purging them for good measure. Have fun piecing all this together.
Don't worry though sir, not everything's changed. You remember Angron, Fulgrim, Mortarion, Perturbo and Lorgar? They're still around, but they're ultra powerful daemon entities chilling in the warp right now.
Oh, P.S. your awesome, huge legions have been split into many tiny little chapters and we ran out of gene-seed whilst you were gone, you could have picked some spare ones up with the milk. (Only one or two would need this heads up) and Abbadon's still around, he's the one of the only ones with a force the size of the old legions, but he's bent on the complete destruction of the imperium right now, so we can't ask him for help.
and P.S.S. look up Tau, 'nids and necrons, welcome back sir