i'm sure there are more spoiler down below but incase anyone wanted more details, i used a translating software so take it with a grain a salt lol.
now the big question, why does sion think parvel betrayed him?
this is a bit iffy...but before sion dies in his previous life, parvel actually found him in time and kills sienna under the rubble (for breaking his promise to give up his own stigmata in return for leaving him and sion alone but sienna obv didn't keep that promise and kidnapped sion to rip his stigmata from him). parvel is happy to be reunited but sion is distraught and crying. sion learned that, the death of all the villagers that took him in as a child was due to him living with them. many people's lives ended because of him and this killed sion inside (survivors guilt).
parvel knew that this was killing sion from the inside, so he told sion to only blame parvel and suffer no more for all the bad things that happened so that sion would live on hating only parvel and not himself. and thus, sion died and parvel followed shortly after(he couldn't live without sion who he loved). and their second timeline began.
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as many have assumed, this is parvel's second timeline. he came to the second timeline when he was a child and witness the blue lightning where he got his own stigmata as a child. in this timeline, because he knew of the future, he purposely hide his stigmata from the moment he got it. he needed the freedom to easily travel around to look for sion rather than being stuck at OG sienna's side being his servant.
he looked for years for sion, the village he lived at, and wherever there might be a glimpse of him. however, years had passed and he was around the age where they last met but there was no evidence that 'sion' ever existed.
in the previous life, sion was adopted by this village that later got wiped out, but that village continued to survive but there was no sion. he was getting more and more agitated, wondering if he'd never be able to find sion again. this is when the scene in ch. 47 happen where OG sienna tries to come onto parvel but he get hella pissed and tell sienna he wants him dead more than anything. (this happened the day before the coronation)
parvel is annoyed what happened the last time with sienna bc he's been trying to keep his hatred lowkey until he finds sion and replace sienna with sion as holy king. but since he had no success in finding sion, he snapped at OG sienna (the cause of sion's suffering) too early but knows if he acts nice then OG sienna will probably let it his previous behavior go.
just as he's having these thoughts he goes to the coronation room (ready to convince sienna to continue to hold the coronation bc he needs sienna to lose credibility on the day of eclipse so he loses support from the people) but the moment his eyes lie on sienna, he gets a flashback to when he told sion before dying together that no matter what form, he will always recognize sion. and this is the end to parvel's side.
hella long but incase anyone wanted to know haha