A fun way for you is to put a major drawback such as poisoning himself if he misses or spraying the poison and potentially hitting his teammates. My father suggested making the item decay and I think the wildemount dormant/awakened/exalted pattern is a wonderful way to do this. Put a specific location where he needs to "charge" the weapon (such as the corpse of the boss he pulled it from) and slowly remove damage from his rolls the longer he goes without charging it. You could even remove the poison option if he goes long enough. Another option is to steer the campaign away from combat, which the weapon is for, and towards roleplay and social interaction. Perhaps as they gain power and thus prestige they have to mingle with the upper class more in order to avoid being labeled as criminals and having their property taken under a corrupt rich persons manipulation of the law.
A fun way for you is to put a major drawback such as poisoning himself if he misses or spraying the poison and potentially hitting his teammates. My father suggested making the item decay and I think the wildemount dormant/awakened/exalted pattern is a wonderful way to do this. Put a specific location where he needs to "charge" the weapon (such as the corpse of the boss he pulled it from) and slowly remove damage from his rolls the longer he goes without charging it. You could even remove the poison option if he goes long enough. Another option is to steer the campaign away from combat, which the weapon is for, and towards roleplay and social interaction. Perhaps as they gain power and thus prestige they have to mingle with the upper class more in order to avoid being labeled as criminals and having their property taken under a corrupt rich persons manipulation of the law.