Since I wrote this as a reply to a comment, might as well share for others. How did it get this long? Σ(  ̄□ ̄||) HUGE SPOILER (READ AT OWN RISK!):
So basically this is a story about reincarnation. Long ago there are 3 Children of God (children who are loved and blessed by God). 1st child who killed his lover. 2nd child who killed her son. 3rd child who killed his parents. Because of their sin, all 3 were cursed by God to reincarnate with dark mana (or dark magic within) and remember their past lives. Once they remember their lives, they will repeat their sins. 1st child will fall in love, remember his lover and kill his lover again. 2nd child will love her child, remember her past and kill her child. 3rd will do the same for his parents. They repeat countless reincarnation like this, basically living in torment for their guilt by killing their loved ones. As you can guess, the 2nd child is our MC Aisha (I think she's the great saintess from 500 years ago who was said will be reborn again), and Abel is the soul of her child she will end up killing if she ever remembers her past due to the curse. The medication MC is taking (as seen in the webtoon) is given to suppress her power and memory so she wouldn't remember. The one supplying this medication is a priest from the temple name Mikhail/Michael (?), who is the 1st cursed child of God. And as may suspect, our MC is his past lover. Michael is planning to kill MC before he falls in love with her again so that he won't suffer the pain of killing a loved one again. The reason why MC killed her child long ago was bcuz her child was in pain/sick and she couldn't help bear to watch him suffer, so to end her child's pain, she killed him. As for the 1st child of God, he himself couldn't remember why he killed his own lover. The 3rd child of God however, watching the 2 suffer from their sins, he tried to break the curse by killing the God himself but he didn't succeed (and ended up getting cursed too, with killing a parent curse). The 3rd child of God was the most favoured and he has the power to Procreate/Create life, so he ended up creating the world for the 2 other child of God hoping for them to break the curse so they all can be free (so basically the 3rd child is the author of the book MC read).
Our poor MC will start stopping taking her medication and that's when her power and memory slowly coming back (she had both black magic and white magic in her body). That's when she realize that she will end up killing Abel if this goes on. She will want to break their engagement and ask ML to kill her bcuz she couldn't kill herself as the curse will rebound any effort of self mutilation. Oh and also she was Janes (in her past life before she dies and got reincarnated and transmigrated into current body, Aisha), the person who guided ML to save the then orphaned Abel. MC as Janes, pleaded to ML to take good care of Abel and for him to promise her to kill anyone who will come to him in the future saying that they remembered their past lives. And ML promised Janes.
And in the current timeline, after MC remembers this, she asks ML to uphold that promise. ML is totally livid and their conversation is so heart breaking. ML refused, but MC said that with the curse she won't be able to stop herself from killing Abel, and she kept apologizing to ML for dragging him into this mess of a fate. She also said that now she had black magic, she could even control ML's mind (as black magic can brainwash people) if she wants (kind of hinting she might command him to kill her using that method if he continues to refuse), but ML kept refusing and hoping they find a way to break the curse together. ╥﹏╥
Anyway, since the spoiler is incomplete and I don't have all the details, some things happened and it's happy ending! They managed to break the curse and finally all three children of God can live in peace. MC and ML got to have their happy ending with Abel, creating a happy family.
So basically this is a story about reincarnation. Long ago there are 3 Children of God (children who are loved and blessed by God). 1st child who killed his lover. 2nd child who killed her son. 3rd child who killed his parents. Because of their sin, all 3 were cursed by God to reincarnate with dark mana (or dark magic within) and remember their past lives. Once they remember their lives, they will repeat their sins. 1st child will fall in love, remember his lover and kill his lover again. 2nd child will love her child, remember her past and kill her child. 3rd will do the same for his parents. They repeat countless reincarnation like this, basically living in torment for their guilt by killing their loved ones. As you can guess, the 2nd child is our MC Aisha (I think she's the great saintess from 500 years ago who was said will be reborn again), and Abel is the soul of her child she will end up killing if she ever remembers her past due to the curse. The medication MC is taking (as seen in the webtoon) is given to suppress her power and memory so she wouldn't remember. The one supplying this medication is a priest from the temple name Mikhail/Michael (?), who is the 1st cursed child of God. And as may suspect, our MC is his past lover. Michael is planning to kill MC before he falls in love with her again so that he won't suffer the pain of killing a loved one again. The reason why MC killed her child long ago was bcuz her child was in pain/sick and she couldn't help bear to watch him suffer, so to end her child's pain, she killed him. As for the 1st child of God, he himself couldn't remember why he killed his own lover. The 3rd child of God however, watching the 2 suffer from their sins, he tried to break the curse by killing the God himself but he didn't succeed (and ended up getting cursed too, with killing a parent curse). The 3rd child of God was the most favoured and he has the power to Procreate/Create life, so he ended up creating the world for the 2 other child of God hoping for them to break the curse so they all can be free (so basically the 3rd child is the author of the book MC read).
Our poor MC will start stopping taking her medication and that's when her power and memory slowly coming back (she had both black magic and white magic in her body). That's when she realize that she will end up killing Abel if this goes on. She will want to break their engagement and ask ML to kill her bcuz she couldn't kill herself as the curse will rebound any effort of self mutilation. Oh and also she was Janes (in her past life before she dies and got reincarnated and transmigrated into current body, Aisha), the person who guided ML to save the then orphaned Abel. MC as Janes, pleaded to ML to take good care of Abel and for him to promise her to kill anyone who will come to him in the future saying that they remembered their past lives. And ML promised Janes.
And in the current timeline, after MC remembers this, she asks ML to uphold that promise. ML is totally livid and their conversation is so heart breaking. ML refused, but MC said that with the curse she won't be able to stop herself from killing Abel, and she kept apologizing to ML for dragging him into this mess of a fate. She also said that now she had black magic, she could even control ML's mind (as black magic can brainwash people) if she wants (kind of hinting she might command him to kill her using that method if he continues to refuse), but ML kept refusing and hoping they find a way to break the curse together. ╥﹏╥
Anyway, since the spoiler is incomplete and I don't have all the details, some things happened and it's happy ending! They managed to break the curse and finally all three children of God can live in peace. MC and ML got to have their happy ending with Abel, creating a happy family.
2021-01-06 10:17 marked
HUGE ASS SPOILER AHEAD!!