I read this a couple years ago and I can't remember which title it was so I hope someone around here can help me.
I remember that it's Draco/Hermione story in Year 7 and a war was about to take place. It started when Hermione went to prevent Draco from getting Dark Mark. He raped her in Forbidden Forest and he didn't go to Dark Lord. After that, he sent a locket or a ring with an owl to her, asking if she wanted to come and have real first time with him. She did go and later they became involved regularly in secret dungeon room. There's a scene I remember that Draco was pouring a blue liquid on her body while she was blindfold and tied up and had his way with her.
In the middle of a story, there's a time she wanted to stop thing between them as she was to send his locket or ring back to him (but she neither couldn't or else he pursued that they shouldn't) but whatever, they were still together and later they were fell in love with each other and it was not just sex anymore. Then the War took place at Hogwarts and Draco forbade her to come out but she came to battle anyway and almost got killed by Lucius but it turned out that she was pregnant and there's a powerful force by her baby's magic shielded her out of the spell. I am not sure that he killed his father or not when Draco found her but Lucius died.
That's all I can remember. I read it from AFF and if it didn't get deleted, it should have still been around. It is complete fic and has around 30+ chapters. Thanks!!