Trench crusade

The blades of the Assassins are imbued with the Supreme Poison. In chambers deep below the surface, generations of young assassins are raised in the dark; fed a diet of scorpions, frogs, deadly mushrooms and even stranger, more noxious things, and generation by generation their tolerance grows. The poisonous blood of these willing vessels is drawn and smelted into a poisonous iron. The iron is forged into blades and deadly spells of slaying layered into each fold of the envenomed metal. Thus the blood of the first generation of Assassins lives to this day, growing more potent with each generation