Oblivion:Attack on Fort Sutch

Quick Walkthrough
Note: This quest does not appear in your journal.

# At any time after completing Dagon Shrine, but before completing Light the Dragonfires, travel to Fort Sutch.
# You will find a group of soldiers battling Daedra in front of an Oblivion Gate.
# Help the soldiers defeat the Daedra.
# Close the Oblivion Gate.

Detailed Walkthrough
Triggering the Quest
Unlike most quests, this does not show up in your journal. The trigger for this quest is the delivery of the Mysterium Xarxes to Martin (part of the Dagon Shrine quest) and the subsequent opening of several Oblivion Gates across Cyrodiil. This particular gate opens at Fort Sutch, which is also the site of a Dark Brotherhood quest, Bad Medicine.

The Path to Fort Sutch
Fort Sutch is located north of Anvil. When leaving the main gate of Anvil, travel along the Gold Road until it begins to bear northeast; look for an unmarked road that branches off to your left and continue along it to the north. This road will lead to Lord Drad's Estate. Once you arrive at Lord Drad's Estate, the road will end; head north-northeast and continue through the countryside. As you start down the hillside, you will see the ruins of Fort Sutch and an Oblivion Gate to the northeast.

Events at Fort Sutch
When you approach Fort Sutch, you will encounter a group of Imperial Guards - including an Imperial Guard Captain - who will request your assistance in defeating the Daedra pouring out of the nearby Oblivion Gate. The final Daedra you will need to defeat will be a leveled Dremora, who will emerge through the Gate as you approach it. When all the Daedra are defeated, return to the Captain. Speak with him and he will tell you to close the gate if you wish, but informs you that he will be staying at Fort Sutch as per his orders.

The Daedra may be a significant challenge, since they will greatly outnumber the Imperial guards. Eventually, once all the Daedra come swarming out, overwhelming the soldiers, one of the guards will scream ''"There's too many of them!" or "We've got to fall back!"''. Remember to come prepared if you want any of the soldiers to live.

An alternative way to deal with the Daedra is to prevent them from spawning in the first place. If you avoid talking to anyone and sneak up on the gate from the east (using Invisibility helps), the Daedra will never go into attack mode. Immediately enter the gate and close it. When you return to the area after closing the gate, the only Daedra that you and the guards should have to face is the leveled Dremora and possibly a stray or two. This approach makes it much easier to keep the guards alive.

The Gate
Approach the Oblivion Gate and enter the Planes of Oblivion. You will be transported randomly to one of four Oblivion Planes (specifically Random Oblivion Worlds 2, 3, 4, or 7). Proceed as you have previously, find the appropriate Tower and close the Oblivion Gate.

Notes
Promotional screenshots for the game depict Imperial Legion Soldiers fighting Daedra in a fort ruin, likely meant to represent this quest. The scene is also featured on a loading screen.
This quest appears to be heavily modeled after the demo of Oblivion that Bethesda had shown at E3 to promote the game's release. Further evidence supporting this includes the fact that the Imperial Legion Soldiers involved in the quest are members of the "Soldiers at Oblivion gates" faction, which was used in the demo and retains the relationships it had with the other E3-exclusive factions, even though almost none of them are still used in-game. Apart from the omission of the E3 factions, other differences between this quest and the demo include several NPCs and creatures being removed, renamed, or replaced by ones more appropriate for the final game (e.g. "Imperial Legionaires" being replaced with "Imperial Legion Soldiers").

Quest Stages