The old thread has been deleted, so here's the walkthrough again...First and foremost you should exhaust all possibilities before you search for answers in this walkthrough, don't give up too easily. If you are stuck in a dungeon, make sure to have investigated it completely and every corner examined carefully. Just running through the dungeons and crying for help at the first dead end definitely is a bad idea and is absolutely unwanted.
So as not to kill all joy for yourself, you really should consult this walkthrough only in the last resort. This exclusively deals with the main quest so as not to reveal all of Ivellon's secrets - other small riddles and side tasks you should find and solve on your own, when you are in the mood to do so.
Furthermore, with this walkthrough I would give away as little as possible - in most cases I just indicate a direction without to reveal the entire solution. The player is supposed to get to the bottom of the secrets by himself after all.
1.1 The Search for IvellonFirst of all you have to find the book that Narina Carvain, countess of Bruma, preserves in her private rooms, in a display case in the corner of the bed-chamber.
Spoiler In the second line of the book you find a name and a city. If that does not help:
Betake yourself to Chorrol, into the house of Casta Scribonia, the great-granddaughter of the book's author.
In the basemant of the house there is an old chest containing a manuscript (among other things) - scrutinize it very carefully.
If you can not unravel the mystery:
Spoiler Concealed in the text there are many "typing errors", double letters. You have to write them out. The outcome of this is the sentence: "My true friend - buried he lies in Cheydinhal". So the next station would be the graveyard of Cheydinhal.
There is a gravestone with a strange inscription - if the solution to the riddle absolutely refuses to come into mind, just wait a couple of game days.
Once you have reached the target, investigate the dungeon. Behind some closed doors that can only be opened by the key from Marcus Scribonia's chest, you will come across a small, longish room. Pay attention to the floor at the left wall, there is a small chest.
1.2 The Cloud TowerAll in all there are three copies of the book "The Cloud Tower of Cheydinhal" to be found, the book can not be obtained from merchants.
Spoiler One of them is in a chest in the dungeons of Cheydinhal.
One copy can be found in a display case in the castle of Cheydinhal.
Another one is in a chest in the Hackdirt Caverns.
Follow the directions in the book to get to the tower.
You will not be able to enter the tower if you have skipped preceding quest stages.
2. Ivellon: The BarracksExplore the level and find the journal of priest Janus, the drunkard. Everything else goes without saying.
With the handwheel in the (initially closed) main room you can open the grate in the south of the dungeon, in this way you can enter the dungeons.
3. Ivellon: The DungeonsExplore the level. Find the bell hammer, the bells and the letter with the instructions how to get into the crypt.
4. Ivellon: The CryptThoroughly explore the level and find the skeleton of a (by now) known person.
In the circular room with three pedestals you need three crystals that are hidden in the crypt.
Spoiler The first one is to be found at the skeleton, in the journal of which contains a reference to the second one.
The third one is in the east of the crypt near the Shrine of Mara. You have to solve a riddle at the stone plate next to the shrine to get this one.
In case you fail to do so: You have to lower the intelligence of your character to 10 or lower by means of alcohol or the "Potion of Folly" and then appear in front of the plate.
The Potion of Folly can be found at the undead magicians and battle mages (among others).
You have to place the crystals on the pedestals in the circular room, however, this only works if you have read the journal of the skeleton before. A secret passage will be opened as soon as all crystals have been positioned in the sockets. From now on you should be able to cope with the quest on your own.
The passage leading to the catacombs is in the room with the Shrine of Mara.
5. The CatacombsGo southward and find the chest with the key at the end of the passage in a small room.
With this key you can open the door in the East of the catacombs. From then on there is no need of further explanation.