- Talk to Jarl Balgruuf.
- Meet Irileth near the Western Watchtower.
- Kill Mirmulnir, a dragon.
- (Optional) Use your new Shout power.
- Report back to Jarl Balgruuf.
Shortly after you return the Dragonstone to Farengar, a scout will approach to inform him that there has been a sighting of a dragon at the Western Watchtower outside of Whiterun. The scout asks you to meet Jarl Balgruuf in the strategy room. Follow her and Farengar up the stairs beside and behind the Jarl's seat. He will tell you to accompany his housecarl, Irileth, as she heads for the western gate. She will recruit several Whiterun Guards along the way.
Follow Irileth to an area outside the west gate, or meet her there. After she delivers a speech to rally her soldiers, follow them west towards the tower.
You will gather near the road close to the watchtower to find the watchtower burned and smoking, evidently signs of a recent attack by a dragon. After a short talk, Irileth will give orders to search for survivors. On the north side of the tower, on or around the ramp leading to the interior, you will encounter a single rattled surviving Whiterun Guard, stammering about what he has just been through. Shortly after hearing this, you will hear several warnings that the dragon has returned. Irileth will advise taking cover against the dragon's attacks and to "make every arrow count."
The dragon, named Mirmulnir, will approach from behind the mountains and follow a dragon's standard pattern of attack. Dragon combat strategies should be employed against him. He will land, fight, and then fly off after losing about a quarter of his health. Once he is wounded to a further degree, he will remain on the ground. This particular dragon is resistant to fire, so arrows, frost or shock attacks, and melee weapons may be your best offensive choices.
When in the air, the dragon will use magical attacks against you or other enemies. These will be fire attacks if you are at a lower level, but may vary if you are above level 20 or so. If his attention is focused elsewhere, it is a good opportunity to attack with a ranged weapon or spell. If he is aiming at you while in the air, seeking cover, such as within the tower's interior, can be a life-preserving tactic.
When on the ground, Mirmulnir has two modes of attack: magical and physical. When on the ground and facing you from a moderate distance, he will use his fire breath attack as long as you are in his line of sight. When up close, he will attack with his claws, which can easily be fatal if you do not keep your health high. If approached from behind, he will beat his tail on the ground; if this hits you, it can do some serious health damage. (As above, types of attacks may vary if you are at a higher level when fighting Mirmulnir.)
The best plan of attack when the dragon is on the ground is to approach from the side while he is occupied with the Whiterun Guards. Attack relentlessly until he flies off again (or, if already seriously injured, dies). Pay attention to the guards because once they're dead, the dragon will likely focus more of his attacks on you, although Iirleth cannot die at this point because she is an essential character.
Once killed, Mirmulnir will disintegrate and release his soul in a fiery blast of energy. You will automatically absorb the soul, allowing you to use the Dragon Shout Unrelenting Force, which you learned during the Bleak Falls Barrow quest. After using the Shout, a nearby guard will approach in awe and exclaim that you are Dragonborn. Some of the surviving guards are hesitant to believe this and argue with him. Irileth haughtily discards it as a myth and walks off to investigate the skeleton carcass, ordering you to report back to the Jarl.
Searching the dragon's body will provide you with Dragon Bones and Dragon Scales. These can be used to forge and improve dragonbone and dragonscale armor once you have the appropriate smithing perk. They make for an excellent source of income at early and middle stages of your life in Skyrim, as you will have opportunities to acquire many more before you can use them in such ways.
A search of the area in and around the tower should reveal one or more guards killed by the dragon. As they will no longer be needing their possessions, you may wish to collect them.
As you make your way back to Whiterun, you should hear a thundering voice boom out "DOVAHKIIN", shaking the very ground. Return to Dragonsreach and report to Jarl Balgruuf.
He will ask you to recount events at the watchtower. After he learns of you being Dragonborn, he informs you that the Greybeards are summoning you to High Hrothgar, and that they can teach you to use your gift. The Jarl advises you to travel to the Greybeards immediately, as the summoning is a great honor. Despite this sense of urgency, however, the Greybeards will be waiting for you whether you embark on your voyage to visit them now, or whether you decide to first explore elsewhere or take care of other business.
If you are not yet a homeowner, recall that you now have the right to purchase property in Whiterun, and may purchase Breezehome from Proventus Avenicci if you have sufficient gold.
For your assistance in slaying the dragon, the Jarl will appoint you Thane of Whiterun, which entitles you to a personal Housecarl, Lydia, a relatively forgiving and respectful attitude from city guards and others, as well as other benefits. He will also reward you with the Axe of Whiterun as your symbol of office. The axe is a leveled weapon that carries a random enchantment effect.
Lydia will greet you if you head toward the front door of Dragonsreach, at which point you can make her a follower by telling her that you need her help.
