That is a lot. So...
- that knight dude was supposed to kill the mad dragon, but killed its lover who was an outsider
- this resulted in the mad dragon no longer had a fate (death)
- to get its fate back, the mad dragon sacrificed its heart to break the causality law
- at the same time og eris had been wishing to disappear
So is current eris the mad dragon's soul? Or a poor bystander causality used to fill in the gaps left behind....;;;;
No, I think the outsider was the mad dragon.
It changed the prophecy so that Jason (knight dude) would slay it instead of another, unnamed dragon, and that unknown dragon turned out to be the mad dragon's lover.
Then that unknamed dragon sacrificed its heart to "regain its fate."
Side note, what is the deal with dragons in this story. Like on the one hand they're apparently sorta immortal* and sound kind of like, possibly good possibly evil forces according to that priest, but also people were and are cool with the idea of Jason killing an unspecified dragon at some point in time.
*Is it just me or did the priest not actually say dragons couldn't kill themselves. He just said that they live a super long time.