Am easier version of Morrowind, in Tamriel.
In Oblivion you go into these hellish places called Oblivion Plains, basically hell. You have demonic soldiers from hell, and there smaller followers. You also get the multiple cities and towns and villages that are strewn across the map. And then Inns all over the place. Basically the map to this game is huge.
On the other end of the stick, untill you get to a high enough level you will encounter only goblins, rats, wolves and deer. Even once you do get to a high level you encounter bears and troll along with the rest of the other lower level creatures.
Then you have the option to join guilds, the Brotherhood of Darkness as one of them. You may also join the imperial legion or the Blades at certain points in the game, giving you some of the only times to get a dai-Katana.
I do like Oblivion and will continue to play it when I am able to.