Born the illegitimate son of Camoran the Usurper and his Bosmer mistress Kaalys, Mankar is the author of the Commentaries on the Mysterium Xarxes, and the founder of the Order of the Mythic Dawn, a Daedric cult dedicated to Mehrunes Dagon.
He has two children, Ruma and Raven, who also serve the Prince of Destruction. Camoran appears to be a "typical" mage; in reality however, he and his children appear to be immortal. It is unknown for sure how old Camoran is, but it is said that he was born in 3E 277, shortly after his father, Camoran the Usurper, died. 
Mankar Camoran was born to Haymon Camoran (better known as "Camoran the Usurper") and his Bosmer mistress. Mankar was born and raised in a shelter for war refugees in the region of Dwynnen in Valenwood. He and his mother lived there while his father Haymon waged a bloody war on across southern Tamriel.
It is unknown exactly when he was born although it was certainly towards the end of the conflict as Camoran was described as a baby in the end of the year 3E 276, which was the exact date of the Usurper's death. Shortly after his birth, his mother (who the other refugees noted performed the birth entirely herself) left the shelter and never returned for her son. It is unknown who raised Camoran after the death of the Usurper. It is also unknown whether or not Haymon Camoran ever knew or cared that he had a child, or what became of his favourite mistress.
Founding the Dawn
Later, Camoran founded a Daedric cult called the Order of the Mythic Dawn. Mankar developed a close relationship with Prince of Destruction Mehrunes Dagon. Dagon granted Camoran his own plane of Oblivion which he shaped to resemble Dawn's Beauty, a vision of how he believed the world would look once he helped Dagon take control.
Daedric invasion of Tamriel
In 3E 433, Mankar plotted to destroy the Septim bloodline and prevent the Dragonfires to be lit, so that the barriers between Nirn and Oblivion could dissolve, allowing Dagon to enter the realm. The Mythic Dawn started by assassinating Emperor Uriel Septim VII's heirs, Princes Geldall, Enman and Ebel Septim. This prompted Uriel to attempt to go into hiding, taking a secret escape route through the Imperial Prison out of the city.
However, Camoran had apparently foreseen this, and had one of his lieutenants, Eldamil, arrange Uriel's own assassination inside the escape route. Though the Mythic Dawn agents succeeded in murdering the Emperor, a prisoner in the Imperial Prison (who is the Hero) was sent away with the Amulet of Kings to Jauffre.
There was one remaining heir to the Imperial throne, an illegitimate son named Martin Septim. Camoran apparently knew this, and had Martin's home city, Kvatch invaded and completely destroyed to kill Martin. Though the city was destroyed, Martin was safely brought to Weynon Priory by the Hero. But in the meantime, Camoran had Mythic Dawn agents attack Weynon Priory and steal the Amulet of Kings.
With the Amulet of Kings, Camoran entered Gaiar Alata to wait for the barriers between Nirn and Oblivion to dissolve completely, while the Hero and Martin collected several artifacts needed to follow him there.
After being victorious in a great battle near Bruma, the Hero was sent to Gaiar Alata to kill Camoran and retrieve the Amulet of Kings. After fighting Camoran in his palace, Carac Agaialor, the Hero defeated him, which caused Gaiar Alata to dissolve.
Mankar Camoran's Paradise, also known as "Gaiar Alata", is a small island realm in Oblivion created by Camoran by using the Mysterium Xarxes. When a member of the Mythic Dawn dies in his service, they ascend to the Paradise. While it appears heavenly, it is, in fact, quite hellish.
In the Paradise, Mankar's Immortal ascended followers are constantly attacked by daedra. If killed, the Immortals are not freed from their hell. Instead, they will be resurrected only to have to endure the process all over again. The only way to escape the Paradise is through a portal called the Forbidden Grotto. To gain access to the grotto, one must gain the Bands of the Chosen. These are only given to people who are highly trusted by Camoran.
Once someone passes into the Grotto, they are never heard from again. It is later found out that the Forbidden Grotto is not a place of salvation, but a torture chamber, from which the only method of escape is removal of the Bands. Such a feat is impossible by conventional methods.
Commentaries on the Mysterium Xarxes
Mankar Camoran's Commentaries on the Mysterium Xarxes is a four-volume set of books written by Camoran. The Commentaries are sought after by those who wish to join the Mythic Dawn. To join it, a potential initiate must find a secret meaning hidden within the books. The player character uses the books to recover the Amulet of Kings from Camoran.
The books are:
- Commentaries on the Mysterium Xarxes: Book One
- Commentaries on the Mysterium Xarxes: Book Two
- Commentaries on the Mysterium Xarxes: Book Three
- Commentaries on the Mysterium Xarxes: Book Four
- In The Elder Scrolls IV: Oblivion, Mankar Camoran is voiced by British actor Terence Stamp.
- Mankar Camoran is able to wear the Amulet of Kings, despite not being a member of the Septim Dynasty.
- Camoran appears in the game as an Altmer, although both his parents were Bosmer.
- When the Hero of Kvatch enters the Forbidden Grotto, Mankar Camoran names some of the planes of Oblivion but relates them to the wrong Princes.
- He cannot be killed at the Dagon Shrine, if he is attacked he will stop his sermon, open a portal and leave.
- It is revealed in his commentaries on the Mysterium Xarxes that he may actually be able to use the Thu'um as he described that he could speak in a new language and after three days he could speak fire. This, coupled with the fact that he can wear the Amulet of Kings, may imply that he is Dragonborn.
- Events of The Elder Scrolls IV: Oblivion