Sirius had an old House-elf named Kreacher at home.
Sirius had never liked it, and it did not like Sirius either. By extension, he did not care much for Hogwarts's other House-elves. The kitchen happened to be the place with the most House-elves in the entire school.
Back when they were students, they had made a Marauder's Map to avoid Filch. The grand excuse was that it would help Remus return to the dormitory after transforming in the Shrieking Shack, but in reality, it was more often used for pranks.
Not long ago, Remus had confiscated it from Harry—clearly, it had gone through an unknown journey. At the time, for some reason, Harry had wandered near the Slytherin dungeons, close to the dock where the first-years' boats landed. Then he had run into the old bat returning from his night patrol. Remus had saved him.
The Hogwarts kitchen was one of the few places not shown on the Marauder's Map. Anyone entering the kitchen vanished from it just as they did upon entering the Room of Requirement, which happened to be not far from the Gryffindor common room.
The last time the Fat Lady had been attacked, Pomona had deliberately not reminded everyone about this, though that was far from the only thing she had neglected to tell others.
She still found it hard to believe that Sirius would betray James. He had specifically bought that motorcycle with a sidecar so he could go to the Muggle world with James. They could have each had their own flying motorcycle, the kind meant for one rider, but he had bought that one instead.
"Who brought Buckbeak to Hogwarts?" Scamander asked.
"The Black family's House-elf," Pomona replied.
"Why?" Scamander continued.
"You just mentioned last year's incident. Did you know that Harry Potter