Actually not eating would not offer immunity to poison as there is such a thing as contact poison which is absorbed through the skin and then spread by the circulatory system.
Yeah, but that's mainly from something like pesticides or chemical spills or something. Like if you are working in a field with pesticides for too long the pesticides can seep into your clothes and then as long as you wear the clothes the toxin is slowly absorbed into your skin.
Hmmm... mind of reminds me about that 'Corrupted Blood' thing that happened in World of Warcraft.
Imagine if there were poisons you could apply to virtually anything.
Add it to food or consumables like potions and when eaten the person also gets poisoned.
Add it to weapons (the blade) and you can poison whoever gets struck by the weapon.
Same with arrrows or darts.
Add it to clothes or armor and they get a slow poisoning over time. Like if you put on a torso armor with poison on it, then 30 minutes after you put it on then you get a poisoned status as if you had eaten poison item... but it never runs out as long as you wear the armor.
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semi-related idea.
a disease that causes damage over time like a poison. but it tends to 'jump' over to nearby things to infect others. items you wear can become infected, items you hold in your inventory may get infected. People near you can get infected. (different diseases spread in different ways with different levels of contagousness).
Adding diseases could provide an added danger to make exploring and moving more of an 'adventure' than just a walk in the park.
Imagine going into the sewers knowing that you risk catching a disease as well as just facing monsters. (be sure to stay away from pools of stagnent water).
Keep plenty of medicines when exploring jungles and swamps (though not sure if they will be here). Also provides real reason why polluting the giant lake is a major crime. See various other lakes that are dangerous to drink and see why that one is so important to keep clean.
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Would make antidotes and medicines a pretty good investment.