The mechanics of the game were... unforgiving. Poison? If you even know how to make a successful poison without killing yourself - you're going to find very little help on 'forbidden skills' like thievery. Hire assassins? Who? Caan you even find an NPC who'll do this sort of thing? Other PCs? Money's useless when you risk losing your hard-earned character. Back stab in their sleep? Good luck getting into their castles, which have real defenses for exactly this reason. Also, how are you going to learn to backstab? Again, forbidden thievery skills means it's the HIGHER-UPs who have them (because no one can stop them, and they're the ones who made the skills 'forbidden' in the first place). They will dodge your attack and then kill you. Which goes back to the 3rd sentence in that quote I guess.
You can wait for the person to go out alone, throw a spell at the person and kill him instantly (funnily enough, viable in game). But then you'll have to hide his soul somewhere, otherwise all his underlings (all exprienced PCs not to be trifled with) will go all out to look for him, and ressurect him. They can find his soul even if it's in the depths of a dangerous dungeon. You could opt to try destroy his soul, since you're going to die anyway. If you can figure out the methods to do this. Good luck.
(What is it called when you hate a game, and love to rant endlessly about it?)
*takes notes*
I guess it also depends on how much power the authority has? This can vary wildly from game to game. Authority may actually mean nothing in one game, and almost completely dictate your IC life in another.