You must be at least 4th level to be offered this quest. Unless you're psychic, you'll have to go talk to Helseth directly to get this quest. There is supposed to be a letter delivered to you, but it never shows up in your inventory. About the only clue you get is a courier from Wayrest delivering something, but when you look, there is nothing in your inventory. This happens along about 3rd or 4th level and after you have completed Morgiah’s quest. There has long been speculation that this was simply an invitation to the betrothal ceremony that you helped arrange, but I suspect that the message is from Helseth, asking you do come do a favor for him.
Prince Helseth (that's him with his feet on the table) wants a letter delivered to Lord Castellian. He'll give you the letter and your instructions the day after he offers you the quest, so be on time. Helseth has found out about some "indiscretions" involving Lord Castellian and a noble lady with a jealous husband. He wants to reach an accommodation with Castellian, who is the most influential of Wayrest's counselors and has the backing to block Helseth's plans (whatever they may be).
If you choose to deliver the letter without reading it you'll be rewarded as promised with a piece of enchanted something or other or a magic item and the information that Wayrest had sent counselors to meet with Lysandus the night before he was killed. Your rep will increase with the nobility and people of Wayrest, including Lord Castellian (go figure -- you help blackmail him and he likes you even more).
If you choose to deliver the letter, but read it, you'll get to fight a few guards (knights and a couple of battlemages). Helseth will still give you the armor and the information. Your rep in Wayrest, however, will take a nosedive. If you're going to read the letter, you'd better turn it over to someone besides Lord Castellian.
If you read the letter and then turn it over to King Eadwyre, your reputation with the Court and nobility in Wayrest will soar, +15 to +20 points at the upper end, with a commensurate increase for those factions allied with the various nobles in Wayrest. The only apparent negative consequence are that Queen Barenziah will not offer you her quest (which is also an optional quest), your rep with Helseth will drop by a few points and he won't give you the information he promised.
I've tried, without success, to turn the letter over to the various nobles at Wayrest and at Sentinel. Barenziah won't take it and Morgiah won't even speak to me. Elysana tries to offer the quest to deliver the robe to Lord Castellian (which makes for some interesting responses when you're asking around since Lord Castellian appears on your list twice and each one elicits different responses). Fast-traveling to Sentinel or Daggerfall in order to turn the letter over to nobles at those locations (who won't take it, by the way) has a couple of interesting consequnces. First, the cost of the trip jumps to over 4 billion GP's if you want to make it before the deadline. Second, when you arrive, you'll find that all of your letters of credit have been converted to cash.
The quest itself is easy enough. Collect the letter from Helseth, take it to Lord Castellian (he's in a house in a town somewhere in Wayrest province), get Castellian's reply and deliver it to Helseth. Easily completed in 2 or 3 minutes (real time).
Cyndassa (The Werewolf)
You must be at least 5th level to be offered this quest.
Cyndassa is in Daggerfall Castle (that’s her with the load of laundry – never see any clotheslines, though – kinda makes you go, “Hmmm?”). She's in the room below and to the left of the stairs leading up to the thrones. Be careful, though. The guards at Daggerfall take offense at people snooping around where they're not supposed to be and will attack you after you leave the room (if your rep with Gothryd or Aubk-i is high enough, they will leave you alone).
Like everyone else, Cyndassa has some information for you, but she wants something from you before she parts with it. She wants you to kill a werewolf. The dungeon she sends you to is random, but somewhere in there is a werewolf that returns to human form when you kill it (normal werewolves just keel over and die). It is her brother and she wants him put out of his misery.
After taking care of this little item, go back to Cyndassa (be careful of the guards) to find out that a letter from the Emperor arrived and was given to Aubk-i. Aubk-i promised to deliver it to Mynisera when she found out it wasn't for her. She suggests talking to Mynisera and will put in a good word for you with the Dowager Queen, who is behind the door on the other side of the stairway.
Mynisera (The Courier)
You must be at least 5th level to be offered this quest. So now you have to go talk to Mynisera and get her side of the story. She's at Daggerfall Castle, too.
Mynisera's room is below and to the right of the stairs leading up to the throne. And the guards probably haven't learned their lessons about messing with you, so they will most likely try to attack you when you open the door.
Mynisera (the lady that looks kinda like Queen Elizabeth II) tells you that she never received the letter (surprise!), but is curious as to how it came to be delivered to Aubk-i in the first place. So she sends you to track down the courier who delivered it. She gives you a ring to prove you are working for her. You have some traveling to do to get to the real courier, but it is not too difficult. Just a matter of timing.
First, you have to speak to the person in charge of the couriers. Mynisera will give you his/her name and location. When you talk to him/her, you must have the Queen's ring. He/She will tell you where to find the courier. From there it is just a matter of being in the right town at the right time. Unfortunately, you will get two different time limits for this one - the date you get in dialogue and the date that appears in your log. Go with the date in your log. As of the v.212/v.213 upgrade, this still had not been fixed. If you go with the time limit from the conversation, the courier will not be there (you will be about a week early).
After talking to the courier (who will give you an item to show to Mynisera), return to Daggerfall and talk to Mynisera again (and beat up on uppity guards again - these guys just never seem to learn). She will give you some interesting comments about Lysandus' burial and about Wayrest. She will also let you keep the item as your reward
Orsinium
You must be at least 5th level to be offered this quest and must have completed the Courier Quest. Talk to Mynisera again and she will give you a letter to Gortwog.
The opening dialogue for this quest is one of the flakiest in the game. You probably talked to Morgiah and did her quest long before tracking down Mynisera (it was Morgiah who told you to talk to Cyndassa and Mynisera in the first place -- remember?), yet the developers use dialogue that implies that you haven't talked to Morgiah yet. Go figure.
Anyway, Gortwog wants to create a free and neutral orc state. Mynisera's letter tells Gortwog that she will support him in his bid if he will give you the Emperor's letter. Gortwog is willing to let you have the letter, but you have to go get it from where ever it is in the bowels of Orsinium. (What? You thought he'd just hand it over to you? Yeah, right.)
Gortwog is in the first big room when you enter Orsinium. If your Orcish skill and Personality are high enough, the guards will leave you alone (sort of). Otherwise, they'll attack you. There are three guards in the room: an Orc, an Orc Warlord and an Orc Shaman, plus an Orc who may or may not come through the door behind Gortwog. At lower levels the Orc Shaman can be pretty tough. They like to fireball you a couple of times and/or turn invisible and try to backstab you. The tables in the room will prevent the backstabbing (because he can't get to you). The Orc and Warlord should be no great shakes. Gortwog will be personable enough and will give you permission to retrieve the Emperor's letter.
Go through the left door at the back of the room (the one the Shaman is in front of). Opening the door will set off an alarm, alerting the critters that you are on your way. If you can get the Shaman or another Orc to step in front of the door, however, it will open on its own without setting off the alarm and you can backstab almost everything in the dungeon since they won't know you're coming.
Go down the corridor (you'll run into your first Orc just around the corner) and through the door at the end.
Follow this new corridor, turning left (south) at the first intersection, until you get to a room. Go through the door on the other side.
Go down to the room with the hollow pyramid and jump into the fountain in the northeast corner. This will teleport you to the landing above the pyramid.
Go up the left (west stairway) and south. An Orc will probably come out of the first opening on the left. Follow the corridor and open the first door door on the right.
Follow the corridor beyond (some orcs and a giant will want to have a word with you while you're passing through) until you get to the door at the end.
Go through two small caves (and their inhabitants) and keep following the corridor down.
Keep going down. Turn right (west) where the corridor T's, then down, through the door and left (south) at the next T-intersection.
Keep going down until you get to a big room with a white pedestal in the middle of it. The letter will be on the pedestal and there will be 2 orcs in each of the rooms to the north and south. The doors open when you get close to the pedestal.
There is a door to the north that leads to a small room with a couple of treasure piles in it. You'll hear a strange sound when you step close to the pedestal. There is supposed to be an alarm that says, "Stop! Thief!" but it doesn't work very well.
The letter tells you that Lord Woodborne of Wayrest has the Totem of Tiber Septim, and Mynisera is supposed to use her influence to get him to give it to the Emperor (and here you thought he was having a torrid affair with one of his subject queens - well, actually he did, but it wasn't with Mynisera and the girl wasn't a queen at the time - more about this in another quest). So now you know that Lord Woodborne had the Totem, Queen Aubk-i knew he had it and that the Totem is missing. Guess who's got it. When you bring the letter to Mynisera, she'll tell you that Gortwog has probably circulated copies of the letter throughout the Illiac Bay, that the Totem should only be returned to the Emperor, and that the Totem will probably seek you out (you should be so lucky as to have it come to you).
Give yourself a pat on the back. You have finished the one of the Emperor’s two quests.
Interlude #1
Returning the letter to Mynisera completes one part of the Emperor's mission. Your prizes for getting to this point? If your reputation is high enough, you'll receive some letters (anonymously, of course) telling you about the Numidium. The number of letters depends on your reputation with the various factions (there are seven of them). The more factions that like you, the more letters you'll get. They all say the same thing. But it's a good indication of how many of the factions really likes you. You'll also receive a threatening letter telling you to lay off Lysandus. And as an added bonus, you get frequent visits from assassins who carry notes telling you to lay off or that you need to be taken care of at any cost. The latter letters are signed "--W". Now who do you know with the initial "W" who might want you out of the way? Three guesses and it ain't Willie Wonka.
Now that you've disposed of one mission, you need to pursue the other -- putting Lysandus' ghost to rest.
Lhotun’s Brother
As soon as you reach 5th level and try to fast travel, you'll get an invitation from Prince Lhotun asking you to come visit him at Sentinel. Once in a great while there is actually a courier, but usually the letter just appears in your inventory.
Prince Lhotun is the young fellow sitting on the floor to the right as you go up the ramp from the entrance of Castle Sentinel. He's a nice enough guy and has information you probably want ("definitely want" if you're going to complete the Main Quest). But, like every one else you talk to, it's a quid pro quo situation. You've got to do something for him before he'll give you the information
Lhotun wants to know what happened to his older brother. Ask about him around town to find out that he was a scholar, died several years ago, drove the King crazy because he didn't want to play with swords, and that the king was awfully happy when he died. After you ask enough people (good practice on that Streetwise skill) and have waited long enough (usually about a week to 10 days), you'll get a letter from an agent of the Underking. The letter will tell you to investigate a certain dungeon for information about the missing prince.
While you're waiting for the letter, talk to people, sit in your inn and cast spells, steal the armor shops blind (there are four of them - two of them extremely high quality) or whatever. The dungeon is supposed to be random, as is the location of the letter you're looking for, but once you find it (and read it), you'll discover that the Royal Parents in Sentinel aren't as nice as they would have you believe. (Is it just me or are dysfunctional families the rule for royalty?)
After bringing the letter back to Lhotun, he'll tell you what he knows about Lysandus. Specifically, that Lysandus was hot to trot for a certain royal sorceress, Medora Direnni, and wasn't entirely discreet about it. And who says this game isn't like real life? Lhotun will also mark Direnni Tower on your map (it's on the big island in Balfiera) and give you something for your troubles. All in all he's the nicest NPC you'll have to deal with, so enjoy it while it lasts.