i killed omar, the giant, before visiting the guy up in shadowmirk. now i have a quest "retrieve goblin key from omar", even though i have this key already in my inventory (actually i have five goblin keys, the green one twice). that means i can't trigger the obelisk in the citadel and thus can't enter its 2nd floor. what a bummer!
still, it's a great game and i've had good fun playing it up until today. i'd be happy to fill in as a beta tester in order to avoid such quest-related unpleasantries in future releases, that we will hopefully be graced with.
