Oblivion:Mythic Dawn

The Mythic Dawn is a cult that worships Mehrunes Dagon, the daedric prince of destruction. They are responsible for the assassination of Uriel Septim VII. Their main objective is to allow Daedra to invade Tamriel by opening Oblivion Gates in order to take control of the continent. 

Joining the Faction
It is possible to join this faction during the quest Dagon Shrine for either a short period of time or permanently (although the latter stops you from completing the main quest). The only real implications of joining the faction are that your character may gain four faction-specific combat lines (see Notes) and you will suffer a large disposition drop with all members of the Blades. Although Baurus (if you kept him alive in the past quest) will give you skill increases, his disposition will be drastically diminished. You will also gain a large disposition boost with all members of the Mythic Dawn faction, who may welcome you with the line 'Greet the new day, Brother/Sister' when approached.

To join the Mythic Dawn permanently, leave Lake Arrius Caverns immediately after talking to the door guard (before talking to Harrow) during Dagon Shrine. Otherwise, you will be forced to leave the faction at a later stage of this quest when it comes time for your initiation.

Faction Ranks
The Mythic Dawn has only two ranks that appear in your journal: "Initiate" when you come to the Dagon Shrine; and "Acolyte" if you decide to kill the Argonian sacrifice Jeelius.

Beliefs and Practices

The Mythic Dawn believe Mankar Camoran to be a prophet of the end times; they follow the teachings of his Commentaries on the Mysterium Xarxes. Camoran is known as the "Master" by members of the cult and was supposedly given the Mysterium Xarxes by Mehrunes Dagon himself. Camoran's son, Raven Camoran, is responsible for potential members, while his daughter Ruma is in charge of initiation.

In order to allow the Daedra to enter the mortal realm for extended periods of time, the magical barriers that protect Mundus from Oblivion must be destroyed. Somehow, the Mythic Dawn learned that the Dragonfires in the Temple of the One, lit by every new emperor during his coronation ceremony, were fundamentally linked to the preservation of these barriers. In assassinating Uriel Septim VII and all of his known heirs, the Mythic Dawn succeeded in extinguishing the Dragonfires, thereby allowing the Daedra under the command of Mehrunes Dagon to enter Tamriel through Oblivion Gates.

When a member of the Mythic Dawn dies in the service of Lord Dagon, they are reborn as an "Ascended Immortal" in Camoran's Paradise.  There they await the day that Lord Dagon takes Tamriel as his own and gives them each a share of his kingdom. In actuality, many find Camoran's Paradise to be a place of misery and torture.

Members
While many of the Mythic Dawn members stay at the secret shrine in the Lake Arrius Caverns, some are posing as regular townsfolk. This is not an issue until your identity is revealed to the Mythic Dawn after your theft of the Mysterium Xarxes during the Dagon Shrine quest. After this, Mythic Dawn agents will attack on sight until the Light the Dragonfires quest is finished.
For information about members of the Mythic Dawn, see Mythic Dawn Agents.

Notes
As long as you are a member of the Mythic Dawn, your character may shout a faction-specific combat line such as "Die, unbeliever!", "For Lord Dagon!" or "Lord Dagon will welcome your soul in Oblivion!" when you perform a Power Attack. When you take damage, your character may also shout "I do not fear death!" or "Paradise Awaits me.".  This can only be heard if the player is a Nord, Imperial, Breton, elf, or a female Redguard. Khajiit, Argonians and male Redguards lack the recorded dialogue.