In battle, the Harlequins use hallucinogen grenades to disorientate their enemies just before they attack. The grenades induce hallucination, paranoia and delirium in their victims, causing them to cower in fear, stare into open space or rant and rave at creatures only they can see. A Harlequin model with hallucinogen grenades uses them when it charges into combat. The paranoia and confusion caused by the hallucinations makes it impossible for the enemy to discern exactly how many warriors they are fighting. When working out if one side outnumbers the other after an assault, the ratio of models is shifted one 'grade' in favour of the Harlequins. This is best shown by the following chart.
Morale checks are taken using the modified ratio by the losers of the assault.
Hallucinogen grenades have no effect against any kind of daemonic creature (including Nurglings, Avatars), Wraithlords, Wraithguard, Dark Eldar Talos and Warp Beasts, Thousand Sons Chaos Space Marines or Necrons; any model with an armour value rather than a saving throw. Tyranid creatures ignore the effects of hallucinogen grenades unless the Tyranid player scores a 1 on a D6 roll.
Designer's note: Basically a creature has to be truly alive to be affected by hallucinogen grenades. Doubtless at some time in the far distant future we'll introduce some hideous monstrosity that should be immune to hallucinogen grenades, so this list is by no means totally exhaustive and I ask you to use some common sense concerning whether a model should be affected by these weapons. If you are in any doubt, roll a D6; on a 1-3 the model is affected, on a 4-6 it is not (roll every time it is attacked with hallucinogen grenades).