Dragon Crisis

The Dragon Crisis was a time when Alduin emerged from the time rift he was banished to during the Dragon War. He, along with many other Dragons, caused destruction and chaos throughout Skyrim. He also revived many dragons in an attempt to restore the rule of dragons over men. However, the Dovahkiin rose and was able to defeat him as foretold by the Elder Scrolls.

The main questline of prominently features the Dragon Crisis.

Background
During the time of the human rebellion of the dragon rulers, three heroes, with help from Paarthurnax, were able to defeat Alduin using an Elder Scroll. They were not, however, able to completely destroy him, but rather send him in a time rift through the Elder Scrolls in the form of a Dragon Break.

Battle of Helgen
Alduin exited the time rift during the Civil War. At the time that the Stormcloaks and the Imperials were fighting over possession of Skyrim, the Dovahkiin was attempting to cross the border of Cyrodiil, only to be captured in an Imperial trap along with many Stormcloaks, including their leader, Ulfric Stormcloak, and Lokir (a horse thief). After they were escorted to Helgen, where their execution sentence was to be carried out, Alduin attacked. In the confusion, the Dovahkiin escaped through Helgen Keep accompanying either Ralof (a Stormcloak soldier) or Hadvar (an Imperial soldier). The pair flees to Riverwood, where family members of both soldiers live.

Death of the First Dragon
After recuperating in Riverwood, the Dovahkiin carries news of the attack to the Jarl in Whiterun. After speaking with Jarl Balgruuf the Greater, the Dovahkiin is directed to Farengar Secret-Fire, who bids him retrieve the Dragonstone from Bleak Falls Barrow. Upon returning the stone to the court wizard a guard reports a dragon attacking the Western Watchtower. Jarl Balgruuf bids the Dovahkiin go with his housecarl, Irileth, and some guards and defeat the dragon. It is here, after defeating Mirmulnir, that the player realizes they are Dragonborn. When reentering Whiterun, the Dovahkiin and essentially everyone in and around Whiterun hears voices coming from the Throat of the World, later revealed to be those of the Greybeards, summoning the Last Dragonborn to High Hrothgar.

Training with the Greybeards
Receiving the news of being a Dragonborn and hearing the call of the Greybeards, the Dragonborn traveled to the small town of Ivarstead and proceeded to climb the Seven Thousand Steps. Entering High Hrothgar, the Dragonborn spoke to Arngeir, one of the Greybeards. Arngeir asked the Dragonborn to demonstrate their abilities on him and the other three Greybeards, and after doing so, the Greybeards presented a test for the Dragonborn. The Dragonborn would have to use his or her new ability on three spectral forms. After completing the test, the Greybeards and the Dragonborn proceeded to walk outside to the courtyard for another test. The Dragonborn immediately learned a new Shout, known as Whirlwind Sprint. After demonstrating the new ability, Arngeir then spoke to the Dragonborn and tells him or her that their training was complete, but a final trial was given by him and the Greybeards to retrieve the Horn of Jurgen Windcaller, located in Ustengrav. The Dragonborn went to Ustengrav and discovered that the Horn of Jurgen Windcaller was not there. A note was on the pedestal where the Horn should have been, but the note contained instructions for the Dragonborn to travel to Riverwood and rent the room in the attic; the note was signed by the name of, "A friend."

Riverwood
After arriving at Riverwood, the Dragonborn went into the Sleeping Giant Inn and requested for the room in the attic from the inkeeper, Orgnar. He replies that there is no such room, and quietly tells the Dragonborn to go to the room on the left. As the Dragonborn walks over to the nearby room, a woman walks over to the Dragonborn and speaks to him or her. She reveals that her name is Delphine, and she was the one who took the Horn of Jurgen Windcaller and left the mysterious note. After a short conversation, Delphine revealed to the Dragonborn that she knew about several Dragon burial sites located across Skyrim, including one at Kynesgrove. She believes that the Dragons are being resurrected, and believes that the next resurrection will happenen at Kynsegrove. She asked the Dragonborn to either travel with her or meet her at Kynesgrove, to discover what was going on with the return of the Dragons.

Battle of Kynesgrove
After arriving at Kynesgrove, Delphine and the Dragonborn rushed up the hill to where the Dragon burial site was, as people were rushing to get inside their homes for safety. After getting to the top of the hill, Delphine and the Dragonborn hide behind a rock as they watch one of the most awe-inspiring, but surprising and disturbing sights in Skyrim's history. A massive, black, scaled Dragon was hovering over the burial site, speaking in the ancient Dragon Language as another Dragon was coming out of the burial site. The massive, black Dragon that was resurrecting the Dragon revealed himself to be Alduin, the World-Eater, the Nordic God of Destruction who was the leader of all of the Dragons on Tamriel during the Merethic Era when they still existed. The Dragon who was being resurrected was Sahloknir. Alduin also spoke to the Dragonborn, telling him or her that they were an embarrassment to the race of Dragons, and that their Voice shined not from Dragonkind, but from his or herself. Alduin then ordered Sahloknir to "slay the mortals," and then as Alduin flew away, Sahloknir began to attack Delphine and the Dragonborn, and a battle ensued. Eventually, the Dragonborn and Delphine were able to kill the dragon, and then the two conversed on what happened, what to do next and for information to be revealed. Earlier at Riverwood, Delphine promised the Dragonborn to reveal everything about herself and what she knew, after they dealt with the Dragonborn at Kynesgrove. After Delphine revealed more information about herself and what she knew, the two discussed on what to do next. Delphine believed that the Thalmor had something to do with the return of the Dragons, and if they did, the Dragonborn could use that information to stop Alduin and the Dragons. Delphine had a contact in Solitude, known as Malborn. The Dragonborn would have to meet Malborn in Solitude and discuss the specifics of the mission.

The Throat of the World
Returning to the Greybeards, the Dovahkiin meets with their leader, the dragon Paarthurnax. Paarthurnax then sends the Dovahkiin to find an Elder Scroll.

Hunt for the Elder Scroll (Dragon)
The Dovahkiin traveled to the Dwemer Ruin of Blackreach, where the Elder Scroll (Dragon) was contained within the receptacle of the Oculory inside the Tower of Mzark. The Dovahkiin extracted the Elder Scroll from the Oculory and returned to the Throat of the World.

Duel atop the World
Once the Dovahkiin acquires the Elder Scroll and travels back to the Throat of the World he/she discovers how Alduin managed to come back to Skyrim. After looking into the Elder Scroll, the Dovahkiin fights Alduin with Paarthurnax and together they nearly defeat Alduin during the Duel Atop the World quest by using the mortal-made shout Dragonrend, the very shout used to defeat him long ago. Despite their best efforts, though, Alduin manages to escape to Sovngarde.

The Final Battle at Sovngarde
The Dovahkiin convinces the Jarl of Whiterun to allow them to use Dragonsreach as a prison for Odahviing, Alduin's right hand. After the dragon's capture, he confesses that some dragons started doubting that Alduin is truly the strongest among them, he then strikes a deal with the Dovahkiin, which is to free him and in exchange he would carry the Dovahkiin to the gate of Sovngarde. After reaching Skuldafn, the Dovahkiin defeats the Dragon Priest Nahkriin guarding the portal, then teleports to Sovngarde. Teaming with the three warriors who first defeated Alduin, the Dovahkiin defeats Alduin in the Battle of the Tongues.

Aftermath
In the aftermath of Alduin's defeat, the rest of the dragons now recognized the Dovahkiin as superior to them and agreed to cease their hostilities, acknowledging the power of their Thu'um and the defeat of Alduin.

However, if the Dragonborn did not kill Paarthurnax, the Dovah will now acknowledge them as their King, with Paarthurnax stating his intention to bring The Way of the Voice to all dragons.

In either case, however, some dragons still act to terrorize Nirn. This suggests that not all dragons followed their leader, and therefore making it possible there were some dragons who did not listen to Alduin.

The Dragon Crisis also had a heavy impact for Miraak's machinations in Solstheim, hoping to fulfill his own agenda of domination over Tamriel by killing the Dovahkiin and claiming his/her soul in order to escape Apocrypha, but ultimately was defeated by his rival and slain by his master Hermaeus Mora, as a punishment for his rebellion against him, and his soul claimed by the Dovahkiin, along with the souls of many dragons claimed by Miraak.