As the name suggests, this raid is set ten thousand years ago in the War of the Ancients, during that catastrophic battle in which Neltharion, Aspect of the Earth, gave in to the corruption in his mind and turned against the other dragonflights. After decimating the blues and sending the others fleeing from the battlefield, he turned the power of the Dragon Soul against demon and night elf alike, slaughtering thousands. On that day the fires within him broke out and as he transformed he took a new name: Deathwing.
This major event has become the next target of the Infinite Dragonflight. One of their agents has been dispatched to steal the Dragon Soul from Neltharion shortly prior to the battle. Without its power even if he reveals his madness he will have no way to stop the other dragons from subduing him before he can cause any harm. Without it Deathwing will fall on the very day that he was unleashed, and a great and terrible evil will be removed from history forever.
As much as the Bronze Dragonflight would like to allow this to pass, they can see the alterations in the timeline that this would cause and have concluded that an alternative history would likely be even worse. To attain the relative peace in the world of Azeroth today the mortal races have overcome tremendous odds: odds that are very unlikely to crop up again. Being almost certain that an alternative Azeroth would be worse than the existing one, even without Deathwing, the bronze's have been forced to keep history as it should have been and send yet more adventurers to the distant past.
Players start off in the night elven camp near the battlefield. The night elven army is preparing to march to the front line. You must go with them and fight the Burning Legion to give the elves enough time. At this stage it is mostly non-elite trash mobs, although the sheer numbers of them can make the encounter very difficult. They mostly consist of Felguard, Felhounds and Doomguard.There is also the occasional eredar warlock, who must be taken down quickly due to the tremendous DPS he can do, and some necromantic Dreadlords who will raise the dead, both night elf and demon, and send them attacking you. After killing 100 demons the first boss appears, in the form of a mighty Pit Lord.
Once he is down you leave the defenders and ride on the back of a bronze wyrm to Neltharion's Lair. After landing you come under attack by a number of black dragons who are trying to stop you from discovering the Earthwarders dark secret. They must be fought off, but a few manage to escape and raise the alarm. You have no choice but to hide in the caverns. The dragon who took you there is unable to come in, as the dragon magic would surely be detected, but he promises to wait outside for the journey back.
After fighting your way through more black dragonspawn, you come upon the black Aspect himself. However the Infinites have managed to freeze him in time and are attempting to steal the Dragon Soul out of his grasp. You attack them to stop them from accomplishing their task, but ultimately one succeeds. Before leaving he uses the power of the Soul to stop you from escaping the cavern, then unfreezes Neltharion so that he will finish you off. Neltharion immediately suspects you of stealing his precious Dragon Soul, and unleashes a flood of lava to kill you painfully so that he might retrieve it. However, thanks to an artifact given to you by Rhonin back at the night elf army, you manage to survive by creating a bubble around the raid, and then create a portal to get out.
You reunite with the bronze wyrm, who gives chase to the fleeing infinite dragon. Eventually you manage to catch up with him, and while the two dragons do battle you must find a way to retrieve the Soul before the infinite becomes desperate enough to use it. He will use it once reaching 30% health, completely obliterating the raid and dragon, which gives you about 2 minutes to find it. The Soul is gripped in his claws, so the only way to get it is to jump, spam right click on it and hope for the best. If someone manages to get it the bronze dragon will swoop down and catch you. If not you fall to your deaths. Once it is retrieved you can use it against the infinite dragon to defeat it.
Fly back to Neltharion, who becomes friendly once he realises that you have destroyed the thief and returned the Dragon Soul to its rightful owner (himself). He quickly leaves to meet the other Aspects, bringing with him all his dragons. Now you just have to deal with the black dragonspawn, seeking revenge for those of their kin whom you slew when you first came. Without their master to restrain them, they attack you. After fighting your way out of the caverns you return to the bronze dragon once again, who returns you to the night elven camp.
Back to the front lines again, in an encounter similar to the first one. But this time the demons are on the offensive and the night elves are struggling to hold them back. You must aid the defenders, making sure that Rhonin, Broxigar, Krasus, Malfurion, Illidan, Tyrande, Jarod and Lord Ravencrest all survive. This will likely require the raid to split up, with a few protecting each of these key members of the resistance. The line must hold for five minutes, and after this the dragons turn up. All fighting stops as demons and night elves alike watch the five dragonflights prepare the Dragon Soul. Neltharion turns it against the demons, then the other dragons, and finally the night elves, causing massive casualties among all three groups. But as a small reward for you returning his Soul to him he lets you live... for now.
After this, congratulations! You have managed to bring a great evil to Azeroth, but in the process stopped an even greater evil. So in the end that has got to be a good thing. You return to the Caverns of Time, where the Bronze Dragonflight praises you for your efforts and showers you with rewards.