The quest starts during your battle against Alduin, after you manage to deplete Alduins health bar.
The Fallen walkthrough will offer additional information regarding the characters you will interact with, and how the plot changes.
Fans of the game, who have reached the third Skyrim act, can also use the Skyrim The Fallen walkthrough below, for tips, tricks and hints regarding the areas they can visit and the side-quests they can start or end.
During this quest, you will have to visit Whiterun and Dragonsreach, depending on the choices you make.
The first objective of the quest appears when you see Alduin falling to the ground.
Objective 1: Talk to Paarthurnax, Arngeir or Esbern
NOTE: The objective may be different; depending on the ally, you choose. You will notice that Alduin is not dead, and he flies away, weakened. You must now choose an ally who can offer further guidance.
Option 1: Paarthurnax
If you want to create a connection with the Greybeards, instead of the Blades, talk to Paarthurnax, and tell him that you want to know where Alduin went.
Paarthurnax tells you that maybe one of Alduins allies can help you, and that you should visit Dragonsreach, a place built a long time ago as a prison for a dragon. Paarthurnax thinks that it is a good place to trap an ally.
Tell him that the Jarl may not approve this, and listen to Paarthurnaxs story regarding Dragonsreach.
Option 2: Arngeir
Travel to High Hrothgar and talk to Master Arngeir who heard your Dragonrend Shout.
Tell him that you have to find Alduin and you will find out that he might be in Sovngarde where he devours the souls of the dead.
Unfortunately, Master Arngeir cant tell you more, but maybe one of Alduins allies can.
You have to travel to Dragonsreach, and try to catch a dragon.
Option 3: Esbern
Travel to the Sky Temple and locate Esbern outside.
He will ask you what happened, and you should tell him.
Esbern also believes that Alduin returned to Sovngarde and, if you let him consume the souls of the dead he will become much stronger.
Additionally, he agrees that you should visit Dragonsreach, but he thinks that it is impossible to convince the Jarl to allow you to use his place as a trap for a dragon.
NOTE: If you continue to talk to Esbern, you will receive another task. Esbern wants you to slay Paarthurnax, which according to the Blade, is responsible for the blood shed during the Dragon War. This conversation starts the second main-quest of the third act, called Paarthurnax.
It is also possible to receive the quest from Delphine; however, you should know that if you dont kill Paarthurnax, the Blades will deny any assistance from this moment on.
Objective 2: Talk to the Jarl of Whiterun
Travel tot Whiterun and find the Jarl inside Dragonsreach.
Talk to him and ask the Jarl to help, by giving you a trap to use it inside his castle.
NOTE: You should know that the Jarls response is different, depending on how you have played the game so far. Additionally, the Jarl may not appear if you lost the Imperial Hold during the Civil War. At this point, there are several possibilities to continue the game.
The Jarl agrees to help you if the Stormcloaks have been defeated by the Imperials in the Civil War, or if they have only one Hold left.
In this case, you can skip the main quest called Season Unending, and start the second part of this quest (see below).
The Jarl of Whiterun is missing being defeated by Jarl Vignar the Revered, who was helped by you during the Civil War. In this case, the Imperials lost the war with your help, and Jarl Vignar is willing to assist you.
Again, you can skip the Season Unending main-quest and play the second part of The Fallen (see below).
Both factions, the Imperials and the Stormcloaks, have more than one Hold left during the war, and, in this case, both Jarls have more important business to attend to and they wont agree to help you; unless you negotiate a truce, which is the objective of the main-quest called Season Unending.
NOTE: Assuming that the Stormcloaks or the Imperials have been defeated, and the Jarl you meet in Dragonsreach agrees to help you unconditionally, you will start the second part of this quest and you will receive a new objective.
Objective 3: Learn the Shout to call Odahviing
Since the Jarl is ready to help you, its time to set up the trap, however to call the dragon, you need to learn a new Shout.
At this point you can opt to learn the shout from Esbern or from Paarthurnax:
Go to Sky Haven Temple and find Esbern inside the library, to learn the new shout. If Delphine is with him, she will ask you to kill the dragon located on the Throat of the World, allowing you to start the main-quest Paarthurnax.
In exchange, the Blades will offer their help in the future.
Visit the Throat of the World, and learn the shout from Paarthurnax. You will also learn that a dragons name consists in three words, thats why a shout also has three words, in this case Od (Winged), Ah (Snow) and Viing (Hunter).
No matter what teacher you visit, you will learn the new shout and you can use it anywhere to call Odahviing, but you wont be able to attack him unless you travel back to Dragonsreach.
Objective 4: Prepare the trap for Odahviing
Fast Travel to Dragonsreach and talk to the Jarl.
Tell him that you are ready to catch the dragon, and then follow him to the balcony.
The Jarl will tell you where to stand and when you are ready use the Call Dragon Shout and watch Odahviing approaching.
Objective 5: Defeat and trap Odahviing
When Odahviing approaches, keep in mind that your objective is to trap him, not to slay him.
You will notice that any attacks (ranged or magic) will enrage him.
The best and fastest way to catch the dragon is to use your Dragonrend Shout that makes him drop on the battlements.
He will start advancing towards you, and you should go back, to southeast.
Make sure that the red dragon passes through the giant chains, and you will complete the objective.
Objective 6: Interrogate Odahviing
Approached the trapped dragon and ask him twice where is Alduin. He will eventually tell you that he fled to Sovngarde to regain his powers.
When Odahviing tells you to set him free, tell him that you are his master now and he must serve you.
To reach Sovngarde, you have to travel to Skuldafn, a temple located near the eastern mountains.
The only way to get there is to fly, which means that you must ride a dragon.
Odahviing agrees to take you there, and as soon as you set him free, you will start the next main quest, called The World-Eaters Eyrie.