You have the task of finding the hidden heir to a throne that sits empty. Tamriel's previous emperor has been slain, and with no true ruler the gates to Oblivion open and demons begin to invade the people and towns of the empire. It's up to you to find the lost heir to the throne and unravel the sinister plot that threatens to destroy all of Tamriel.
Oblivion is one of those games that people keep boasting about because of the vast world you get to explore. But mark my words, if there was no vast world, Oblivion would be forgotten. Apart from exploring the world, there are no other good features in the game. The combat is composed of clicking and blocking and requires no thinking behind it. You can get through the entire game just with the minor healing spell that you start with at the beginning of the game. Leveling up is pointless and the atrocious enemy scaling system means that enemies level up to your exact level every time you level up. You can complete the game at LV1 because of this reason. There are few dungeons and caves worth exploring as most of them are generic and contain generic items. There are only a few caves where you can find famous equipment mentioned in the lore. In my opinion, Bethesda should have made more detailed dungeons and caves with more unique loot instead of a hundred with random loot and generic design.
The story isn't anything special. Daemons (or Daedric) invade the world which spawns these Hell gates known as Oblivion gates all over the country and it's your job to stop these attacks by going into these gates and removing the sigil stone from their towers. Thing is, many of these realms of Oblivion are generic and often resemble one another. The Oblivion gates outside cities can be closed so you can get troops to help you in the final battle but the thing is, getting their aid is optional and in reality, you only ever have to close two Oblivion gates. The one outside of Kvatch and the Great Oblivion gate at the battle near Bruma. You don't need the aid of guards from towns to help you since you get Militia if you don't get guard help. So in reality, the main story is quite short if you avoid closing Oblivion gates (I completed it in four hours as a Level 1 Crusader).
I could go on more but I only have 50 characters remaining.