The reason he brought up Camilla's regression because
Spoiler!
He had been regressing when Camilla dies. The reason he is regressing because his fate and Camilla's fate are intertwined. He occupied role where Camilla should have, first child of the Duke's family. Dorman or Havel didn't know about his regression. It was a completely mistake. They will compensate him will making him a reaper after his death because his destination was he** after the death. Jayner is actually the leader of Khan assasination guild, it seems that he didn't know about Camilla beforehand so that's why he took the contract to kill her.
I like to post spoilers for the stories I find interesting because I don't have much time to read novel due to busy schedule
you will find me in most romantic historical manhwa comment sections 
you will find me in most romantic historical manhwa comment sections 
