The War of the First Council was a war started due to religious conflicts between the allied Dwemer and Chimer. The conflicts then turned to war and eventually led to the legendary Battle of Red Mountain.
The event that sparked the war was Dagoth Ur, head of house Dagoth, bringing evidence of the Dwemer "grand project," a project to build a new god and a deadly weapon by utilizing the Heart of Lorkhan, which they found beneath the Red Mountain. This project was being led by Kagrenac, the Chief Tonal Architect of the Dwemer. Affronted at this act of mockery of the Chimeri gods, the Tribunal (the queen and generals of the Chimer) urged their king, Indoril Nerevar, to go to war.
However, Indoril was troubled and went to the dwemer to ask their King, Dumac, whether this was true. According to the book The Battle of Red Mountain and Nerevar at Red Mountain Kagrenac was angered and asked Nerevar "who he thought he was to judge the affairs of the Dwemer," and that the project has been hidden from the dwemer King Dumac. Because of this, Dumac claimed that his people were innocent of any wrongdoings.
Nerevar was still troubled, however, and went to Holamayan, the sacred temple of Azura, for a pilgrimage. There Azura spoke to him and told him that the Dwemer are indeed building a new god, and that it must be prevented at all cost.
Nerevar went back to the Dwemer one more time in hopes that a negotiation and compromise may preserve the peace they held. However the two friends Nerevar and Dumac quarreled bitterly; Nerevar insisted that the Dwemer stop their worship of the Heart of Lorkhan, while Dumac, still unknown of the project, defends his people by saying that they shall not relinquished their ancient belief just as the Chimer won't cut their ties to the Daedric Princes of Oblivion, thus breaking the alliance and leading to war.
The exact events of the war are unknown, as there are various conflicting accounts on what happened. The books The Battle of Red Mountain and Nerevar at Red Mountain tell of similar events but differ at the end. According to those books at the Battle of the Red Mountain, Nerevar drew most of the Dwemer armies to the fields where they were met by his generals and queen, while Dagoth and Nerevar went to the Heart chambers by secret means where they met Dumac and Kagrenac, after the battle between Nerevar and Dumac in which left both of them collapsed from the wounds and draining magic.
This is where they started to differ from each other, The Battle of Red Mountain said that Kagrenac turned his tools upon the Heart and in that instant the dwemer disappeared, Dagoth Ur claimed that Kagrenac has destroyed his own people.
Nerevar then ask his queen and generals what to do with the tools, and a decision was reached where the tools would be kept in safekeeping. Nerevar agreed but made all of them take oath to Azura that they would never use the Heart in the same way the Dwemer intended.
As they went to the chamber to retrieve the tools however, Dagoth Ur refused to hand them over, finally the tools were taken by force. For years after Nerecar death, they kept their oath. However Sotha Sil, one of the Tribunes, had studied the tools and came with a vision of peace; a world ruled by the Tribunal, and so they went on a pilgrimage to the Red Mountain and used Kagrenac's tools to become gods. As they completed the rituals, Azura appeared, angry at their mockery of her and claimed that someday Nerevar will return to punish them and make things right, and cursed the Chimer so they turned into the Dunmer.
Nerevar at Red Mountain, tell again of a similar tale but it differs that rather than Kagrenac using the tools and making the Dwemer disappear, Azura appeared and showed how to use the tools to separate the power of the Heart from the Dwemer. The Tribunal was tempted by the Heart's power and killed Nerevar. However ultimately the Tribunal became gods and the Chimer were changed into Dunmer like the book The Real Nerevar, and War of the First Council Tell of a different tale. According to those books House Dagoth sided with the Dwemer and managed to get the Orcs and the Nords as their allies with promises of lands and booty, although the Dwemer was still defeated.
And The Five Songs of King Wulfharth tell another version of these events, albeit a more controversial one. According to this book, Dagoth Ur went to the Nords and told them that he knew where the Heart of Shor was, in Nordic religion Lorkhan was known as Shor and was greatly revered. And so the Tongues, master of the Thu'um summoned the 'ghost of Shor' and Shor then revived King Wulfharth of Atmora. And so they marched towards the Dwemer and Chimer in hope to recover the Heart. However they were tricked by Dagoth and as soon they got there they were slaughtered by the Dwemer and the Chimer.
Despite the various conflicting accounts of this war, there are some things that we do know for certain; Which are:
- The Tribunals became gods by using the Heart of Lorkhan and the Chimer became Dunmer afterwards.
- Dagoth Ur disappear after the Battle of Red Mountain only to be only heard of again by the time of the Third Era
- The entire Dwemer race disappeared after the battle; whether this means that they achieved what they wanted or failed to use the Heart of Lorkhan is uncertain.
- After the battle on 1E 668 the Red Mountain erupts and the eruption became known as 'Year of Winter in Summer' by the Nords and 'Sun's Death' by the Khajiits. (Pocket Guide to the Empire, First Edition: Morrowind) Although some said it was caused by the defeat of the orcish god mauloch (The Battle of Red Mountain)