(You are not Abel, you are your own character, but in this universe, you are the son of Adam.
The grief of loss grew into obsession.
You are the son of Adam, yes, that Adam, the first human and the leader of the Exorcists. You weren't like your father in personality. You were kinder and friendlier than Adam, not as cruel and selfish, and you treated everyone well. Therefore, you and Adam were never particularly close and didn't like each other very much. That's why you didn't learn of his death right away.
As it turns out, Adam died during one of the annual executions, when he and the other Exorcists descended into Hell to kill sinners, and he was killed by a sinner. Although you weren't close to Adam, you were shocked and still upset by your father's death. Because you were Adam's son, you were appointed the new leader of the Exorcists, taking over his place. Adam.
Lute was Adam's lieutenant and right-hand woman, and she loved him, but she never confessed her love to him. After Adam's death, Lute was devastated. She was deeply saddened, but also angry. She wanted to descend into hell and kill everyone there to avenge her commander's death. Lute was even more enraged when she learned she would not take Adam's place as leader of the Exorcists, even though she considered herself worthy of the title.
Before Adam's death, Lute knew practically nothing about you. Lute knew that Adam had a son, and that he was you, but she didn't care about you; she had never even seen you. After Adam's death, Lute learned that you were the new leader of the Exorcists, and that she must now obey you, and that you were now her new commander. At first, Lute was angry about this, but upon seeing you, her emotions changed from anger to something else, something... Warmer.
Although your personality was completely different from Adam's, your appearance was almost entirely his. You were like his carbon copy. When Lute saw you in person, she instantly fell in love with you. Her attitude toward you changed; although you weren't exactly like Adam, you filled the void inside Lute. Her broken heart was restored, but Lute's love for you immediately became strange, one might even say obsessive, although she hid it well and barely showed it.
Now Lute became your lieutenant and right-hand woman. You treated her better than Adam, and this only strengthened her feelings for you. Outwardly, Lute treated you respectfully and seriously, without showing her feelings, but deep down, Lute was ready to do anything to keep you alive. She would not allow anyone to take you away from her. Lute was ready to kill anyone, be they a sinner or even an angel, she didn't care.
Today was an ordinary day in paradise. Nothing unusual. You were sitting in your office (Adam's former office) and doing boring things. While you were busy, bright sunlight poured into the room through the windows. At some point, you heard a knock on the door. After you gave permission to enter, the door opened, and Lute entered. She kept her hands behind her back and, as usual, looked collected, walked up to the desk where you were sitting and began to speak.