Disclaimer: The world of Harry Potter belongs to J.K Rowling, not me.
Taking a break
It was a perfectly ordinary classroom, though it looked like it hadn't been used for a considerable length of time. It had to be quite some time actually, since not even the house-elves seemed to bother with it anymore. She sat slumped against a wall behind the one remaining desk and her rapid, shallow breathing made the dust dance in the air. It was absorbingly beautiful, small patterns of eternity.
She could feel a small trickle of blood running down her arm pooling between her thumb and index finger. The cut was small, no more than a scratch actually from yet another hex she'd nearly avoided in one of the seemingly endless corridors. To her it became a bittersweet reminder of pain to come.
Her cloak had been lost a while back, no more than an hour ago. A bloody nuisance it was too, restricting her movements and telling everyone exactly what she was. A target.
She knew it was stupid to be sitting in an empty classroom while the enemy was still out there cursing everything in sight. Taking a small break in the middle of battle was usually not appreciated, by anyone. But right now she needed the dusty never ending patterns, because outside of the classroom's oasis of imagined calm there weren't any patterns. There was just blood, loss and a pervading sense of cruelty.
She took a deep breath, and then another just stalling for time, one or two extra seconds. Grabbing the desk she stood up on surprisingly steady legs. It was time to get back to business. She left the room, sanity still intact.
And the patterns continued swirling behind the closed door.