Long has the question of truth been pondered. Long has this been a folly few recognise in time. A killer, a soldier even with a sword is one thing. But a killer who thinks he has found a definite truth, which he decides to fight for, is the most dangerous man in the world.
Another real world thing. White tea. Can only be picked two days a year, the two days before the flowers blossom. Could be a similiar plant that...is the deadliest poison known, cure known diseases or psychosis, or a potent herb that just tastes awesome.