I own nothing, including this prompt idea.
Hermione was sitting in from of the rattling writing desk in the drawing room of Grimmauld. She knew if she opened the roll top, black smoke would come billowing out and spinning about... and she knew what form it would take. Him. Always him. She would stare into his gray eyes as he systematically cut her down word by word. She remembers the things it said to her last time she gave in to weakness and opened the desk. All for a glimpse of him. Because in this war, there was no other way to see him. He was gone, and she was alone. People rarely even visited here anymore. Harry and Ron had insisted she stay behind, stay safe and plan for us. She laughed again. It wasn't safety. It was a prison cell... a dingy, dark, musty old prison cell.
"How could you possibly believe I would love you? I thought you were intelligent. An heir like me... and you, nothing more than a poor little girl who knew nothing of magic for most of her life. Tragic really. You think I really stopped thinking you were a mudblood little girl? A rich popular bachelor is supposed to love the little bookworm just because she saved my life? no, it was pity and nothing more."
There was more, there was always more. She reached out to the wall and touched his name on the tapestry. Still Black as night, alive. Sometimes that was all it would take to calm her. But not today. Today she needed to see his face. Even if it was spouting off pureblood supremacy. But to hear his voice, to see his face and to know he was alive... That was what she needs today. So she reached out and flicked her wand whispering alohomora.
The black smoke billowed out and slowly took shape. It was almost a game the boggart played with her. As if it knew that it wasn't just him turning on her that she feared. No, it was losing him at all. So she watched as his form shaped up... rising slowly from his perfect shoes, wrapping around his legs in the finest slacks, always black. Then his chest and arms, crossed, tapping his wand as the smoke swirled around his neck and up his face. A smile at first, always a smile... that perfect beautiful smile. She should shout it now. Riddikulus. But she won't - she never does.
The boggart was in full force by the time Sirius walked in. Luckily he was the one to find her the first time she had done this. He steps next to her and wraps an arm around her, same as he does every time. When she finally curls into his side the boggart flashes to Sirius and he banishes it before it starts talking as she cries in his arms. He made sure that they were the only two able to access the room after the first time she was standing with his cousin Draco. No one else needed to know what she begged him to forget. Same as always, he poured her a firewhiskey and said nothing, it wouldn't help anyway. She never talked after he would find her. They would just sit in silence. He tried asking once if they were together. Her breakdown that day made him never ask again- it wasn't worth causing her pain. Today that changed. She shot back the rest of her glass, and turned to him and held it out "Did I ever tell you why?"
"No kitten, you never did" and he filled her tumbler back up.
"hm. one day I will. Maybe today. Maybe in a few drinks."
"No rush kitten. some secrets are best told only at the devil's hour. I'll be here"
From there they sat in silence and drank together. Molly would have a fit, so would most of the order. But this was their ritual, it was nothing short of sacred to them, a ritual cleansing of pain. It was a ceremony he began when he first got blown from the family tree and as the years passed, more and more voices added to his pain. Now, he would hear the echoes of his own voice in the boggart, you made the family proud- a true Black through and through. He would feel the dementors and watch the light fade from the Potter's eyes. His own demons. But he knew the girl across from him had demons too, so he welcomed her into his space.
The clock in the hall let out an eerie three notes. She laughed. "I guess it's time now. devil shall have his bargain and all that"
"give the devil his due"
"you know Shakespeare? I guess that's not so surprising. No time like now I guess. Do you remember the diadem? when we went to find it?"
Sirius hummed and reached over and filled her tumbler one final time. It was obvious she'd need it, that day wasn't pleasant.
She took a long drink and looked at Sirius, and told him about how her boggart obsession started- when Harry sent her to Hogwarts for the diadem. Sirius had helped smuggle her in, map and cloak aiding their journey to the room of hidden things. They climbed and searched and laughed together. There were wardrobes from years past, clothing left behind that Sirius took great joy in putting on and continuing to search. She would look over from her pile and there was Sirius, twirling about in a dress from some girl's Yule ball- turns out pink really brought out the best of his features. She laughed so hard that she slipped and slid down her current mountain of forgotten treasures. When she landed, there was a mirror in front of her showing her a future she never told anyone she wanted. Reflecting back at her was her family, at least the one she had wanted. Standing behind her, arms wrapped around her stomach was her object of infatuation from the time she caught him crying. Draco Malfoy, holding her around her swollen stomach... a toddler at her side, a perfect mini Draco. And so it began- her need to know he was alright. Her obsession with a future that will never happen.
Throughout her tale, Sirius stayed silent. Who was he to judge demons and love?
They never talked about that night again. They never really did talk about any of their nights drinking firewhiskey. Something in that night had helped her though. She started to come in for her firewhiskey observances. He always set out her glass, just in case. And that's how they passed the devil's hours of the war. Drinking firewhiskey in silence and pretending it didn't happen the next day. She would research and make plans for the Order then heal those who found their way to headquarters. He would venture out and act out her well-laid battle plans, sometimes talking Kings into bringing her with.
Then the call came. All wands to Hogwarts. The battle was long and hard won. She doesn't remember most of it by the time the adrenaline wears off, but that's probably for the best. There are bodies everywhere, both sides lost so many. Too many.
She just keeps moving all night. The castle is full of celebrations, but she stays out to help the wounded and arrange the dead. The moon is high in the sky when a hand taps her shoulder.
"Devil's hour kitten, why break tradition?"
And that's how he found them- sipping firewhiskey next to the Black Lake, covered in blood and dirt.
She looked at Sirius, eyes wide. That's how it always started. "I... I can't Sirius. not today. please, not today. I can't."
He leaned in and whispered "Kitten, it's him. No mirror, no boggart."
Tears were rolling down her cheeks as she looked over his shoulder, waiting for the boggart to talk, to cut into her. "Granger. It is you. No one knew where you were. I was... they were worried."
"yes, that's obvious."
She started laughing, stood up and walked around him before finally poking his nose. "You're real."
He just looked over at Sirius, wondering how much she already had to drink if she was poking his nose. Sirius shook his head and walked away, leaving the firewhiskey. Draco focused back on her and replied "yes I'm real. why wouldn't I be?"
She pushed her glass into his hand and sat down by the firewhiskey again, grabbing Sirius' old glass and downing it in one gulp. "you know, I've been told that some secrets are best told only in devil's hour. Care to hear a secret about my boggart of Erised Malfoy?"