Actually, if it takes more than one minute to take the contaminated blood out (ALMOST impossible, mind you.) it's gonna reach the heart, causing irreversible damage, and most probably death, pretty sure even good med nins can't do that, and about the bad and mad med nin, no one is dumb enough to kill a person for poison when the snake is right in front, just grab it's neck, and well, extract the poison from it's fangs... then comes the making an antidote thing, yes, that's possible, but this game is mostly about PvP, so man made poison? some natural poison, pretty sure there will be herbs that heal all this so "Antidote" in shinobi form, making the game so realistic as to the point where you can find a poison and develop a cure, that's kind of unnecessary, just introduce a herb that cures poison, or med nin npc in towns (and normal med nin) can heal you with their healing jutsus and stuff to remove poison, real simple.
Follow @SLO_MMORPG