Mehrunes Dagon

Mehrunes Dagon is the main villain in The Elder Scrolls 4: Oblivion, and one of the sixteen Daedric Princes, demonic deities who each have their own parallel dimension to rule over, which are collectively known as the "Oblivion". Mehrunes Dagon, who embodies war and destruction, is the most evil Daedra prince of all, and his plane of Oblivion, the "Deadlands", resembles Hell and is inhabited by an army of demonic creatures. His goal is to take over the mortal world, which he has attempted several times.

During the events of Oblivion, a cult called the Mythic Dawn is attempting to summon Mehrunes Dagon and opening gateways into his plane of Oblivion throughout the kingdom. Their plan involves destroying the royal bloodline by killing King Uriel Septim and all his sons, which they succeed in except for one, his illegitimate son Martin. Before his death, the Emperor frees a prisoner in the palace dungeons (the player) and tells them that he saw them in his dreams and want them to find Martin to stop the Daedra invasion.

The hero finds Martin, and together they lead a campaign to destroy the main Oblivion gates and gather the artifacts needed to stop the Mythic Dawn. Eventually, they gain access to the cult's headquarters in the alternate dimension of "Paradise", and kill its leader Mankar Camoran. After that, the last thing left to do is for Martin to be officially crowned as the new Emperor and light the sacred "Dragonfires" in the Imperial City's temple to stop Dagon from appearing in Tamriel. However, Mehrunes Dagon is summoned into the middle of the city before they can do so, and as a last resort Martin sacrifices himself inside the temple to summon a giant flaming dragon to destroy Dagon.