I am envious, I wish my AUs caused deeply cinematic and detailed visions of a future that could never be.
At the moment we don’t have the full story but it seems
Saving Haurchefant leads to Thordan succeeding at Azys La, which allows him to temper the dragons. Given the screenshots we’ve seen I think we can speculate what happens next.
Thordan also tempers Hraesvelgr and Nidhogg, who we defeat at the Steps of Faith. Taking their eyes Thordan powers himself up even more and tries to kill the WoL. He fails, the souls of the dragons consumed by him are freed, and the tale ends with these events being remembered like they are in the real timeline.