Breaking the Siege of Kvatch

Overview
Faction: Main Quest Prerequisites: Deliver the Amulet, Find the Heir quests Quest Giver: Any surivor of the Kvatch attack Reward: Sigil Stone, based on character's level. Bonus:

Walkthrough
At the base of the hill of Kvatch, speak to one of the survivors. You learn that the few remaining guards are still fighting near the city gate. Head up the path and you will eventually reach three guards and their captain. Speaking to him will let you know that Martin, the heir you are looking for, is trapped inside the city. You can head inside the city now and go inside the chapel and speak to Martin, but he won't come with you until all people go, and they won't go until the captain gives the all clear order.

Note: This Mission is best attempted at a lower level (1-5) and should be one of the main priorities when you start the game. Although it is not impossible when you are at a higher level, it is still considerably harder as your allies all wear the same armour reguardless of your own, and your enemies are levelled and can easily kill the guards. Scamps are a lot easier to face at this stage than Spider Daedra due to your own, and allies vulnerability at certain stages in the mission.

Into the Gate to Oblivion
Head into the Oblivion Gate that stands outside the city gates (stand near it and press "space," or "A" Button for 360; it works like a normal door). Once you are inside, the first thing you will see is a burned body and a whole lot of magma. All of a sudden scamps (or other level-dependent creatures) will spawn and start attacking you, but you will get some assistance from one of the surviving guards who went in before you did. You can tell him to stick with you, or get out. The choice is entirely optional but it is suggested that you let him come with you, because you will need all the help you can get.

Start out by heading to the left and following the path. Your objective will be the large towers in the middle. Along the way you will encounter several more level-dependent monsters. Either way, watch out for the red plants and small things on the ground as they will hurt you and your allies, if you chose to bring them.

Once you are inside the towers, kill the monsters and head upstairs. Once you come to the rooms with the moving pins to the left side of the wall, take the most left door and you will come to walkway that leads to the other tower. In here, head upstairs and you will see one more survivor in a cage. Ignore him, since you will be attacked by yet another Dremora. After killing him, loot his key and speak to the survivor if you want.

Taking the Sigil Stone
Head back into the first tower and go through the door on your left by using the key you just obtained. From here on, it is simply a matter of fighting your way upwards through the Daedra and Scamps in your way. Upstairs, take the Sigil Stone to close your first Oblivion gate. Once done, the building will start to collapse, but you will be deposited outside the now-ruined gate before you are destroyed along with it.

Back at Kvatch
Head back to the Captain and speak to him. He will congratulate you by saying he knew you would do it. Follow him into the burned-out city. Follow him into the church (there will be a few more Daedra along the way, but again, they are no match for such a skilled archer or swordsman as yourself). Now that the coast is clear, the guard will start evacuating the survivors. Once outside the city, you can speak to Martin Septim to continue with the main quest or head back into the church to continue with the optional second part of The Battle for Castle Kvatch by speaking to the Captain.

Shorter Summary
Enter into Oblivion through the fiery gate. Once inside, you discover a hellish world surrounded by lava. The basic procedure of deactivating an Oblivion gate is: Climb the central tower, find the keys to open the right doors, and take the Sigil Stone at the top of the tower. Note that throughout Oblivion are semi-rare ingredients, especially Bloodgrass. Take this chance to collect as much as you can, so that you won't have to make any special trips into Oblivion when in need.

Journal Entries
Speaking to Savlian Matius:
 * Savlian [sic] Matius asked me to help close the Oblivion Gate outside the ruins of Kvatch. He sent some of his men into it, but they never came back. I should let him know when I'm ready to help.

After agreeing to help Matius and his men:
 * I have agreed to help Savlian Matius of the Kvatch Town Guard and his men as they attempt to reach some survivors trapped in the Chapel of Akatosh inside the city. He is willing to lead his guardmen back into the city to attempt a rescue, but the enemy have opened an Oblivion Gate across the entry to the city.

After discovering that at least one survivor was taken into Oblivion:
 * At least one survivor of the assault on the Oblivion Gate has been taken to the large tower within Oblivion. I need to search for him there.

After finding the survivor imprisoned and speaking with him:
 * I found the prisoner in Oblivion. He told me I need to reach the top of the largest tower and look for the Sigil Stone. But I will need the Sigil Keeper's key to gain entry into the Sigil Keep.

After taking the Sigil Stone and closing your first Oblivion Gate:
 * I have closed the Gate by taking the Sigil Stone that anchors it within Oblivion. I should tell Savlian Matius that the way into Kvatch is now open.