Great Sigil Stone

A Great Sigil Stone.

The only catch is that it comes from a Great Gate, like the one opened outside Kvatch.

This is where all the Aid for Bruma quests come in handy. Completion of those sends one or two soldiers per city to Bruma. If you haven't done the quests already, do them now, for at least three cities.

After explanation of all of this, Martin asks you to talk to the Countess of Bruma and to tell her to meet him in the Chapel for a council.

Go speak to her, cycle through all the options, and then head towards the chapel.

When you get inside, wait for the Countess and Martin to finish speaking.

Speak to Martin to learn that three lesser gates must be opened before a Great Gate can be opened. Then talk to the Countess and tell her the time for battle is now.

Leave Bruma from the East gate, and stand with the soldiers just waiting.

If you stand there too long, go inside Bruma (the city) and then right back out--that should fix it. When Martin and some other soldiers get outside, follow them down the path and to a circular area.

What you're going to be doing here is fighting a heckuva lot of monsters. They'll pour out of the first gate, and your job is to help to kill them all and to make sure that Martin doesn't die.

While you're fighting these enemies, you'll receive notices like "the second Oblivion gate has been opened." Just keep fighting until the Great Gate opens.

Also, make sure you loot the bodies of the enemies if they have things that you want to loot (like the Spider Daedra, who carries Silk and Venin, which are valuable alchemy ingredients), as they will disappear. They may not all do so, but I noticed a few bodies disappearing before I could loot them, so it's just as a preventative measure to help you that I say this. :)

You have about 15 minutes to complete this mission.

Assuming that this gate is NOT randomly generated, go just inside the gate that opens once you enter the realm of Oblivion from the Great Gate. There should be a door at the bottom of each tower on either side of you. Go in the right one, though, like I did.

Your goal is to get to one of the bridges that are in front of you, just beyond the second set of towers. So go in the right tower, and flip the switch and ride the Corpse Masher up.

Then go up the ramp and exit through that door. Go straight across, and through that door. Turn right once inside, and exit through that door. Go straight across through that door, and go down the ramp, exiting through the door there.

Save IMMEDIATELY. You can jump across the gap here, but it's very tricky and you will probably have to do it more than once.

Head up the left path until you find a tower door marked "World Breaker Guard." Go into the door and all the way up, activating the Gate Control switch. Now hurry back down across the bridge which the tower's door faces.

If you have time, loot the bodies of the dremora here, they have some good loot.

Head into the tower that's about halfway down the bridge. From here, you know what to do, as most of these Sigil Stone Fortresses (what I call the one tower in each Oblivion gate that houses the Sigil Stone) are all just about the same.

Loot the sigil key from the Sigil Keeper--he'll spawn near the door to the north of the room. It's the door you need to get through. So once you have the key after he's dead, go on through that door.

Head through the door that is at the top left of the room. Then just head on up the ramp in the room. Then into the door marked Sigilum Sanguis. Make an immediate right into the first door-opening you see, and continued to head on up.

Grab the Great Sigil Stone and wait.

Go talk to Martin when you get out of the gate. He'll say that a great victory was won, and that he now has what he needs to make a portal to Camoran's Paradise so that you can get the Amulet Of Kings.