There are places in the universe where the barrier which separates the immateriam from the warp grows thin here psychers face more peril from the use of their powers.
Firstly
In the void (interstellar space) all psychers must roll an additional dice on a threshold check this does not add to their power and only has any effect if it or another dice rolled rolls a nine.
Crossing the barrier into the immateriam decreases all threshold checks by three if a sanctioned Psycher or five if a Sorcerer, must roll an additional dice on a threshold check for every dice they roll this shadow dice does not add to their power and only has any effect if one of them or a power dice rolls another dice rolled rolls a nine, Sorcerers may if they take there time convert one of these Shadow dice into a power dice. Passing into the deep warp as one would on a ship in jump grants two shadow dice to each power dice but once again sorcery can convert one of these to a power dice given ritual preparation.
Secondly
On planets there are places where the veil is as thin as well, most of these feel haunted or unnatural even to non psykers and if a psychic power is used an extra shadow dice must be rolled to enhance the risk of perils of the warp. In some cases these sites are able to focus psychic activity but this is almost always minor and effects sorcery or unsanctioned Pychers rather than Sanctioned ones. The proper ritual can enhance this significantly.
Ginger