Oblivion:Umaril the Unfeathered (quest)

Quick Walkthrough
This quest only becomes available once you have downloaded the Knights of the Nine official plug-in.
# Launch an Attack on Garlas Malatar and destroy the Dark Orb.
# Defeat Umaril the Unfeathered in his physical form.
# Cast The Blessing of Talos and defeat Umaril in his spiritual form.
# Return to the Priory of the Nine to complete the questline and receive the reward.

Detailed Walkthrough
Garlas Malatar
Make your way to Garlas Malatar and meet with the other Knights.  You may choose to have them wait or launch the attack.  Essentially your choice makes no difference, for they will all head into the ruin when you enter.  Once inside jump down to the open area.  Activate the switch on the left pedestal to open the three gates (ideally it is best to kill off the Aurorans in this area before activating the switch, as opening the gates will cause more Aurorans to come in or your Knights to scatter wildly, running into the new unlocked areas in search of more themselves).  Once ready, you can either go through the gate on the bottom level or head up the staircase.  The bottom gate is the shortest direct route to the next zone, if you head up the staircase take either passage and then head left up another staircase and follow to the map marker.

thumb|left|The Orb is shattered and time is frozen
Enter the door to the zone Ceysel.  Make your way through to two locked gates.  Activate the switch on the wall between the gates to open them.  Go through one of the gates and you'll emerge in a large room with a glowing black sphere called the Dark Orb in the center up on a platform and many Aurorans surrounding the room.  Until you destroy the Orb, the Aurorans will keep resurrecting (they show a white healing spell type flourish as they stand back up at full health.) Since your Knights are not similarly immortal (with the exception of Sir Thedret), you will want to destroy the Orb as quickly as possible if you want the original named Knights to survive (and if you don't want to be overwhelmed by them once they've dealt with your followers).  Follow the path to the right, up the stairs, and you will find the Dark Orb.  Activate the Dark Orb to destroy it.  It will explode and freeze time in that room, all Aurorans and your Knights will fade from view.  Slightly back west of the Orb is a switch on the bottom of the right arch, activate it to open up a staircase back down to the lower part of the room and the entrance to Umaril.

Battle with Umaril
Proceed north to the door and make your way through the passages to a large room with a shallow liquid pool in the center.  As you enter, the room will light up, the passage back will be blocked with energy, and a staircase will rise.  Umaril's physical form, an oversized Auroran, appears.  Your holy destiny awaits you.

After the battle, be sure to grab Umaril's sword before casting Blessing of Talos (there will be a chance to grab the sword a second time, doubling your gain).  You can take as much time as you like exploring and collecting loot before finally casting the spell although you are limited to that room alone.  Once you cast Blessing of Talos, turn to the center of the room to watch events unfold.  You'll be transported to the sky above the Imperial City with Umaril attacking you.  Finish him and his legend for all time.  After this battle, when you are falling to Nirn, Umaril's body and his sword will be falling with you.  You can target it and take it for a second sword, however, be careful not to land on it when attempting to do so or you will take falling damage, which will probably kill you.

Priory of the Nine
thumb|right|Sir Thedret delivers the praise of your knights
After falling for some time, you will be transported to the basement of the Priory of the Nine.  Sir Amiel will speak to you and explains what now will happen to them, then watch them all disappear. Sir Berich will remain if you have not already spoken to his ghost. Speak to him too and he will depart.

As soon as you are done talking to the ghosts of the former Knights of the Nine and leave the basement, Sir Thedret will run down the stairs to find out where the voices he heard were coming from. Upon seeing you, he is overjoyed and engages in conversation. According to him, when you went to fight Umaril in the spiritual plane, the remaining knights defeated the last of the Aurorans, and set out to find where you went. They then found your body beside Umaril's, and taking you for dead buried it in the Priory undercroft so the enemies of the Nine would not know you were killed in battle. Being the one to bury you, he can barely restrain his joy at finding you alive and runs upstairs to tell the knights what has happened.

Follow him outside, and you will find him giving a speech to your fellow veterans of the battle (along with new recruits, if you lost any knights during the raid). He will bless the Nine on the Order's victory, and the Knights of the Nine all give you one last hurrah before returning to their new life at the newly restored Priory of the Nine. 

Rewards
If you now activate one of the tombs of the Knights in the Undercroft, you will receive a blessing consisting of a semi-permanent 5 point Fortify Attribute effect.  The effect only appears in your list of Active Effects (there is no on-screen icon), and the associated attribute does not show up in green on your list of attributes.  The blessing will last until you activate one of the other tombs (only one of the blessings can be active at once).  Because this blessing acts as an ability (like the Oghma Infinium), it counts against the 100 point attribute cap when leveling up, so it is important to switch the blessing off of an attribute if you are about to level up and want to increase the attribute over 95.  However, like the Oghma Infinium, this ability can be used to buff a stat permanently above 100.  The blessings are:

:
:†   The reward is changed to +5 Agility.

There is also an armor stand in the Undercroft that previously held the Cuirass of the Crusader in the Priory of the Nine quest.  It is designed to hold and prominently display all of the relics.  If activated, it will offer a selection involving the relics to either "Place All Relics", "Take All Relics", or "Swap Relics". This also repairs, recharges and converts the Crusader's Relics into their level-appropriate variants, i.e. if you got the items at level 5, but are now level 25, placing them on the stand then removing them will mean you now have the level 21+ equivalents of the same items.

You can ask any knight to travel with you and act as a follower.

Notes
As soon as this quest appears in your journal, you are given the rank Divine Crusader in the Knights of the Nine faction.
After the quest, people may start referring to you as the Divine Crusader when talking to you.
When this quest is finished, The Prophet disappears from the Priory, and is not seen for the rest of the game.
It is possible to enter the ruin prior to starting this quest. You can clear out the first few Aurorans in the first section, but you will not be able to advance any further through the ruin.
The best way to keep your Knights alive is to head straight for the Dark Orb. The sooner you trigger it, the less time Aurorans have to kill your Knights.
Sir Thedret is the only Knight of the Nine to have the essential flag. Any other Knights can be killed during this quest, and will be replaced by a generic Knight of the Nine. 
After completing this quest some of the damage done by the Aurorans is reversed.  The chapels in Anvil, Bravil, and Cheydinhal are restored, and replacements (Amragor, Aron Verethi, Beem-Kiurz, Eris Senim, Esbern, Inius Colus, Kinther, and Selene Duronia) for the slain priests (Laralthir, Avrus Adas, Marz, Uravasa Othrelas, Hil the Tall, Gruiand Garrana, Ohtesse, and Trevaia, respectively) appear in the chapels.
Even though Umaril's soul is supposed to be destroyed in the final battle, you can still capture it in a soul gem.
It is possible to obtain two copies of Umaril's Sword. After Umaril is defeated in the spirit plane, you can quickly grab the second sword before you begin to fall.

Bugs
 
There is a workaround though; Switch the view to 1st person and attempt to sit. The view will change to 3rd person. Do not press any button. The view will then switch back to 1st person after about 10 seconds and you will be "sitting". When you get up, the view will switch to 3rd person. Wait for the view to switch back and you will have successfully sat down.
  
 

Journal Entries