Talal Provides said:
"Shits and giggles" is not a valid reason to use a psychic power and risk The Perils of the Warp in Dark Heresy. We're supposed to be looking for signs of daemonic taint, and not by causing the 6000 people that occupy the block in the hive city we're in to become possessed by Khorne and become extremely hostile, just because you thought it would be funny to flood an informant's kitchen with rats and roaches while they were trying to find something to eat.
Actually, it is a valid reason, since most of the fun in Dark Heresy comes from things going horribly, horribly wrong.
That's one of the many reasons the alternate Psychic Power system (first presented in Rogue Trader and later officially added to Dark Heresy rules via the
Ascension supplement) is such a great change. With the three different "levels" you can attempt to manifest powers at, the ever present risk of absolutely horrible things happening simply from trying relatively low-key powers is effectively eliminated - no more are the days of attempting to use telekinesis to call a weapon to your hand (minor psychic power) and accidentally becoming a daemonhost in the process. Taking a hit towards your ability to manifest powers in exchange for immunity from psychic phenomenon/perils of the warp, and the ability to
automatically generate psychic phenomenon in exchange for extra psychic "oomph" behind your abilities makes it a lot more fun to be a psyker (and of course the middle level works like the original system, albeit with some minor streamlining).
The truly horrific consequences tend to be saved up for moments when it would actually be significant to the unfolding narrative (desperate battles and the like) - the risk of being hauled screaming into eternal oblivion for pulling what amounts to a parlor trick tends to put something of a damper on the desire to use those parlor tricks after all. So "shits and giggles" is back on the table as a valid motivation for a lot of somewhat pointless psyker tricks, yay!