Sirius looked around the room, grinning and shaking his head. He turned around to see her still standing there and rolled his eyes, pulling her inside and closing the door behind her.
"I have no idea. We found it a couple years ago. Apparently, if you walk past the stretch of wall three times, thinking about what you need- whatever you need," he explained, wandering around the room and taking in his surroundings, "it just appears. And apparently this was what we needed. Or so the room thought. Personally, I was just trying to get somewhere that we could talk without getting interrupted."
He looked down at the couch, wondering if it was strong enough to hold him up, and then sat on it heavily. When it didn't collapse under him, he grinned, patting the cushion next to him that had some strange stain on it.