Could someone inform me if they know of a reason (beyond the basic mechanics of the system) as to why Shadow in the Warp would have no impact on sustained psychic powers? To me, it seems that while a Psyker may not have to refocus his energy in order to keep his power going, the sudden intrusion of the Shadow in the Warp would throw him a bit off his game.  As per RAW, a maintained power requires no focus power test, and thus no penalty when the Shadow in the Warp appears.

I was considering implementing a house rule saying at the first appearance of the Shadow, a re-focus power roll would be required, or alternately reducing the original activation roll by 20, mainly because that 'feels' right.  Much like a Fear rating- once it's there, you check it once; you don't have to keep re-checking because a Tyranid Warrior is hopping in and out of range each turn.  I wanted to run it past the superior fluff experts and number crunchers on these forums to see if I'm the only one that thinks the RAW feels funny.
 

P.S. I feel like this has been covered previously - apologies if it was, searching for "shadow in the warp" and iterations on the term resulted in pretty crap search results

It does feel funny, you're right. Also Achilus Assault has a short text on SitW, it pretty much govern the shadow of planets under assault and says the (planet-wide?) modifier can range from -10 to -50.

Alex

Thanks for the pointer, I apparnetly totally missed that on my first (and second) readngs.  For my current purposes, that will do quite nicely.  Perhaps I'll toy with the implementation of requiring a 're-focus' test when the enemies aren't quite so entrenched on the planet.