Oblivion

The fourth in the Elder Scrolls game series.

Oblivion is a single-player game that takes place in Tamriel's capital province, Cyrodiil. You are given the task of finding the hidden heir to a throne that sits empty, the previous emperor having been killed by an unknown assassin. With no true Emperor, the gates to Oblivion open, and demons begin to invade Cyrodiil and attack its people and towns. 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.