Great game but not as good as Fallout 3.
Anyway the story is that u are a prisoner and the emperor who sons have recently been murdered is now trying to escape and a secret passage out of the city through the sewers just happens to be in your cell forcing them to bring u with them.While in the sewers the emperor is assasinated by an evil group called mythic dawn who are trying to release all of the daedra on cyrodil by opening the oblivion gates which u have to stop while also protecting the emperors long lost son martin.
The game has lots of other features like lot of swords,staffs,maces,warhammers,shields,armors,and clothes you can also custom create your character and his skill and the game has a massive map.
Basically if u dont have Oblivion get it.