After completing the Orcish Emancipation quest, you may receive an anonymous letter if you have a high enough reputation with certain factions (you may actually receive several messages from different groups if you are really well-liked). These missives will provide some information about the Totem of Tiber Septim and Numidium, and how Tiber Septim used this gigantic brass golem to forge his empire more than four centuries ago. He or she who holds the Totem controls Numidium and with it, Tamriel's fate.
Similarly, some one of these people or groups may reveal information about the Mantella. The Mantella is a massive green gem that once served as the "heart," or power source, of Numidium. It cost Tiber Septim's battlemage his own "heart" to create it. The Totem alone is worthless; the Mantella must be placed within Numidium's body to activate it.
The following list provides the factions that may send you a letter, along with the minimum reputation required before each faction will send you a letter:
IMPORTANT: Due to a bug, most of the factions or persons mentioned in the table above will not send you a letter, regardless how much reputation you have with them. This behavior is very likely caused by the game engine's inability to allocate reputation data correctly. Only three factions or persons will send you their letters in the end (assuming you have the required amount of reputation with them). These are shown in the table below:
This isn't really a quest, but it provides useful information about the Totem and the Mantellan Crux.
After you have received any one of the letters, you can embark on the optional quest Elysana's Betrayal.
This quest will end after you have completed the final quest of the main questline if you never acquired the required reputation to receive any of the three letters.
Most of the listed factions or persons will not send you a letter, regardless of how high your reputation with them is.
DFQFIX addresses this. While it was not possible to get the remaining factions to send letters, the Merchants faction was added to the list; now you may receive letter 1 from them if your reputation is at least 50.
When you receive a letter, its arrival will be announced by one of the following:
You approached [sic] by a young page who smiles in recognition and does not ask your name before he hands you a letter addressed to you. To all of your questions, he merely responds with a blank look and a smile.
A letter is pressed into your hand. You spin to see who gave it to you. You catch a glimpse of livery that vanishes into the crowd.
A page steps forward saying "Letter for you (player's name)," and hands you a note.
A courier steps up to you with a letter in hand. "I was told to give this letter to someone fitting your description," says the courier. As you take it, the courier turns and walks quickly away.
Reaching into you pack for something to eat, you spy a note. It wasn't there before.
A redfaced courier startles you with a cry of "Letter for (player's name)! Hey that must be you. Here, take this. Gotta go. Other deliveries to be made.[sic]