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 animosities between the allied Dwemer and chimer that sparked the war was at first renewed when Dagoth Ur, head of house Dagoth bring evidence of the dwemer 'grand project', the project to build a new god and a deadly weapon by utilizing the Heart of Lorkhan they found beneath the Red Mountain the project was led by Kagrenac the High Engineer of Dwemer. Affronted at their act of mockery of the Chimeri gods, the tribunal (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 is true, according to the book The Battle of Red Mountain and Nerevar at Red Mountain Kagrenac was angered and ask Nerevar 'who he thought he was to judge the affairs of the dwemer'. And that the project has been kept hidden from the dwemer King Dumac, and thus Dumac claimed that his people is innocent of any wrongdoings.
Nerevar was still troubled however and went to the Holamayan the sacred temple of Azura for a pilgrimage, there Azura spoke to him and tell him that the Dwemer is indeed building a new god, and said that it must be prevented at all cost.
Nerevar went back to the Dwemer one more time in hope that a negotiations and compromises may preserve the peace they finally had. However the two friends Nerevar and Dumac quarrel 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 believe just like the chimer won't cut their ties to the daedric princes of Oblivion. And so the alliance broke and they went to war.
The exact events of the war is unknown, as there are various conflicting accounts on how it 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 hart 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 magics.
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 as safe keeping. 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 tool however, Dagoth Ur refused to hand them over, finally the tools was taken by force. For years after Nerecar death, they kept their oath. However Sotha Sil one of the tribunal has studied the tools and he came with a vision of peace a world where the tribunals are patron, and so they went to a pilgrimage to the red mountain and used Kagrenac's tools to transform themselves to gods. As they completed the rituals, Azura appeared and angry at their mockery of her and claimed that someday Nerevar will return to punish them and made 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 that Kagrenac used the tools and made the dwemer disappeared Azura appeared and show how to use the tools to separate the power of the heart from the dwemer. And that the tribunals was tempted by the heart power and killed Nerevar. However ultimately the tribunals became gods and the Chimer was changed into Dunmer like the book The Battle of Red Mountain states.
While 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 through managed to get 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 the tale of another different version of this 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 the Dwemer and Chimer in hope to recover the heart.
However they were tricked by Dagoth and as soon they got there tehy were slaughtered by the Dwemer and the Chimer.
Yet another different version came from The Secret Song of Wulfharth Ash-King
According to this book, the Dwemer and Chimer joined forces against the nords led by Shor (Lorkhan), and at red mountain they were met by Nerevar, Dumac Dwarfking, and Alandro Sul immortal son of Azura, the nordic forces and Lorkhan was defeated however.
Despite the various conflicting accounts of this war, there are some things that we do know happen for certain; Which are :
1) The Tribunals became gods by using the Heart of Lorkhan and the Chimer became Dunmer as the consequences.
2)Dagoth Ur disappear after the Battle of Red Mountain only to be heard again by the time of 3rd era
3)The Dwemer disappeared because of their failed attempt to utilize the heart of lorkhan, which led to the victory of the falmers in the War of the Crag
4)The Nords was beaten on the Battle of Red Mountain leading to Jurgen Windcaller a master of the thu'um to create the way of the voice that decreed that thu'um should not be used as tools of war.(Tablets of High Hrothgar, A Pocket Guide to the Empire 1st Edition : Skyrim)
5) 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. (A Pocket Guide to the Empire 1st Edition : Morrowind) Although some said it was caused by the defeat of the orcish god mauloch (Varieties of Faith in the Empire)
- War of the First Council (Book)
- The Battle of Red Mountain
- Tablets of High Hrothgar
- A Pocket Guide to the Empire 1st Edition : Skyrim
- (A Pocket Guide to the Empire 1st Edition : Morrowind
- Varieties of Faith in the Empire
- The Secret Song of Wulfharth Ash-King
- The Five Songs of King Wulfharth
- The Real Nerevar
- Nerevar at Red Mountain