The combined psychic prayers of Grey Knights are focussed in battle to constantly confuse and wrong-foot their enemies, blinding their corrupted senses with the shining light of their faith and resolution.
Each time an enemy unit fires at a unit of Grey Knights it must check if it can see them. Roll 3D6 and multiply the result by 3, giving a number between 9 and 54. This is the number of inches the Grey Knights can be spotted at, and if the unit is within this range then firing is conducted normally. A unit which fails to detect Grey Knights misses its chance to fire at an alternative target in the confusion. Guess range weapons and ordnance weapons fire as normal but double their scatter distance if the Grey Knight targets are outside the spotting range rolled. Normal Night Fighting skills and equipment such as searchlights have no effect on this power but units which include a psyker can re-roll the dice and accept the second result instead. Actual Night Fighting conditions override this rule.
Errata — Chapter Approved: Codex: Daemonhunters Q&A (v1.0): Yes, the Space Wolves' ability to re-roll their dice when trying to spot the enemy in Night Fight missions also works against the Grey Knights' Shrouding.