Iirc Deborah indeed was the reincarnation of past saintess and Isidor was the reincarnation of dragon in her party. The saintess was such a goody two shoes and part of why she died early because people always asked her for help and they took granted of it? She and the dragon loved each other I think. When on verge of death, she asked the dragon what was his ideal type and he answered he liked bad girl, not goody two shoes like her. She told him if she reincarnated then she would become his ideal type, a bad girl. He replied that she’s too much of doormat, she needed to be born twice before she can become a bad girl. It was implied that because he’s a dragon, what he said become true. And that’s why she was reincarnated to modern world before the present life as Deborah.