As in Death Aid, each killer could have his or her own 'style' - say, have 5 members trying to kill the most people, each having a certain style of murder - maybe one drowns people in toilets, another stuffs people down garbage grinders, another uses antique corkscrews... see if the team realise that the killings are linked despite the different m.o.'s - kind of like, 5 serial killers all at once, all striking repeatedly in the same night. Could be very interesting if ran well
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This is how I would play it as a Judge campaign, by the way - this idea could, as I said before, make a good campaign for perps to participate in so long as the players don't mind thier characters inevitably ending up in the cubes...