Arena: You assemble a magic walking stick so you can kill and then save the Emperor.
Daggerfall: A dozen different people get the same giant robot and kill each other with it. Also they don’t.
Morrowind: You kill an undead leader and destroy an old artifact, thus dooming your entire province to be squished by a rock.
Oblivion: You convince a man to break a really valuable gem right before he dies.
Skyrim: You and a bunch of ghosts yell at a big lizard until it dies so you can save the world. Either your country is ruled by racist assholes, or is conquered by racist assholes. You decide.
ES Online: You absorb the soul of one of your friends so you can kill a god who’s evil because he absorbs the souls of people.