Garret Snakebark's death set off an investigation through Azkaban. More than a few inmates mentioned seeing a Grim in the hallways on the night he died and they were actually listened to this time, as the man's neck looked like it had been torn apart by a wild animal. Teams of Aurors searched the prison from top to bottom and the warden even spoke with the dementors to ask if they knew of such a beast in their domain.

Sirius had often wondered how the Ministry was able to communicate with such unholy monsters, but for now, that was a mystery that he wouldn't pursue. For now, he just needed to wait until the investigation died down before he could make another move and plan who would be next. It ended up taking nearly two months with the Aurors even investigating their fellow guards to see if any of them could have done it. In the end, it couldn't be solved and they closed the case.

During that time, Sirius did pick out his next target. For now, he would stay away from the inmates with strong family connections outside as their deaths would kick up the most fuss. It was probably because he had a family that was the reason the investigation into Garret's death took so long. That was also why Sirius decided that Lonnie Crane should be the next one to die.

Crane also wasn't a marked Death Eater but was a large part of Voldemort's operations to remove muggleborns from society. A half-blood himself, the man kept an ear to the ground in the muggle world for cases of accidental magic in muggle communities. From there, he would kidnap children who had yet to receive their Hogwarts letters and deliver them to Death Eaters. He never did get blood on his hands, but by association, they were stained up to his eyeballs.

Lonnie slipped up when he kidnapped the bastard child of a Wizengamot Lord. Not a major one, but one who kept track of the children he had outside of his marriage and forced an investigation into the matter which led to the arrest of Crane. During his trial, it came out that he had kidnapped nearly a dozen children other than the bastard of the Lord. He would be a resident for many years to come, but most importantly, he had no family to miss him.

Sirius started making his rounds among the medium-security prisoners, making sure inmates saw him, and watched him growl at those he considered marked for death. On the night that he planned for the man's death, he ran into an unwelcome surprise. As he arrived at Lonnie's floor, he spotted a dementor making its rounds through the halls.

The dark-cloaked horrors would often make their way through the halls instead of just moving up and down the pit or the outside of the walls. It was their fortress, so they did as they pleased. However, they generally avoided the hallways as that was the path the Aurors took and Sirius believed the Patroni that escorted them left some kind of marking that was like wolf piss to a rabbit.

The cell bars were solid steel, with mechanical locks and a metal bar for extra insurance. As had been shown many times in the past, charms and enchantments degraded quickly around dementors, so magical doors and locks would not hold long. Additionally, the doors had such locks so the dementors couldn't enter the cells and feast on the prisoners or kiss them just because they could. They weren't supposed to of course, but it was hard to punish something that couldn't be killed, and they probably knew it.

That gave Sirius an idea, and once the dementor had passed Mr. Crane's cell, he padded over and slipped inside. Instead of killing the man outright, he slunk over to the corner of the sleeping man's cell and watched him twitch in his sleep with the presence of the dementor so close. From the darkest point in the cell, he began to growl.

It took nearly half a minute for the man to wake up, and Sirius desperately hoped the dementor hadn't moved on yet. He could still feel a cold aura but had no idea how far away it had gotten. Lonnie slowly woke up and looked towards the door as he had heard the growl and seen Sirius as a dog outside his cell on previous nights. As he stared at the door, Sirius growled again.

Lonnie's head snapped to the corner where Sirius was sitting and his eyes widened as he stepped into the light from the window. He was still just an Irish wolfhound, but he was skeletal in some areas, completely ungroomed, and haggard. Lonnie jumped out of bed and backed towards the cell door.

"No, no!" he cried out. "It's the Grim of Azkaban! It's here to kill me! Guard! Guard!"

The guards couldn't hear him, they were up at the top of the prison, sheltered by half a dozen Patronus charms at this time of night. Sirius stalked towards the man, growling and snapping his jaws, as he called out in despair begging for help from any who could hear.

Part of the design for Azkaban was that all of the cell doors were staggered. No one had a room that could look into another. Sirius just continued to frighten the man he began to despair of his fate.

The despair is what Sirius was looking for, and like a beacon, it drew the dementor back to his cell for a tasty snack. With his back to the door, Sirius watched as the black-cloaked figure reached into the cell with one decrepit arm and held the man in place against the bars. Sirius sat on his hind legs and watched what happened next cheerfully with his tongue hanging out. With its other arm, the dementor pulled back its hood to reveal something resembling a skull.

Sirius had seen illustrations in his family's library of what a dementor's face looked like, but this defied all descriptions. It was a skull but had no holes for eyes or nostrils. It had no jawbone either, just a small hole where a mouth should be. He could see something, like a distortion in the air, originating from Lonnie's being, and being sucked into the dementor's mouth.

Lonnie had stopped struggling and was just looking at the face of the dementor frozen with fear. With its free hand, the dementor tilted the man's chin up in what almost looked like a romantic gesture before something happened that Sirius did not expect. It almost looked like a spider was going to crawl out of the dementor's mouth as six mandibles came out of the hole in its face and latched onto the man's mouth and chin, holding him in place. Lonnie began screaming as silver light passed from his mouth into the maw of the dementor.

Once the man's soul had been completely swallowed, the dementor released him and he slumped to the floor. It lingered for a moment as it focused its attention on the dog watching it eat its meal before it gave a short shriek, covered its face with the hood, then departed. If Sirius had to guess, he would have said the dementor was thanking him.

From there, he just needed to leave some evidence that this had been his doing as well. Lonnie was still alive, technically, just devoid of a soul. Sirius went ahead and bit into the man's leg, hard enough to leave teeth marks, and dragged him back to the middle of the cell. From there, he scratched at the man's chest until he had enough blood on his paws to leave footprints as he departed the cell. Once he was out, he gave a triumphant howl before running around until the blood had worn off, then returned to his cell.

Sirius smiled over the next few weeks as rumors filtered their way down to his level. Just because no one's doors faced each other, didn't keep people from speaking to each other. There was no time outside the cells, so the only interaction people received with human beings was to talk to each other during the daytime or to the guards when the food came twice a day. However, they weren't the most talkative unless you had a bank vault to give bribes for extra services.

Not surprisingly, at night, no one wanted to go close to their cell doors. After the incident with Lonnie, very few wanted to get close, even during the daytime. He heard from his neighbors that the Grim was in league with the dementors, luring them into place for a meal. That Lonnie had been targeted because his crime involved children, and that was something extra deserving of death to the spectral canine. All of the rumors were a delight to hear, but Sirius was quick to squash down that feeling of happiness and focus on his task.

Every few months, he would select a new target and kill them. Sometimes he would just kill them in their sleep, other times, he would feed them to a dementor. That became common enough that if a dementor spotted him in the hallways, it would tail him to his target, knowing it could get a free meal. When that happened, it sometimes took quite a bit of work to get them to the dementor at the door. Not surprisingly, they seemed to prefer dealing with the Grim of Azkaban than with an actual dementor. However, he always got them there in the end, and the soul-sucking wraiths always gave him a shriek of thanks before moving on. Every time he left a calling card of some kind to show this kill had been his.

At the end of his third year, he had killed fifteen of Voldemort's supporters, surpassing the number of people he had supposedly murdered to be put here. He hadn't killed any of the lifers yet, but he had all the time in the world for them.

As he was going to be there for life as well, he had spruced up his cell a bit as well. Not even the ministry could touch the contents of his vault while he was alive, so he would occasionally ask the guard to bring him something nice in exchange for gold.

They would bring him a bank draft for some exorbitant amount, and he would sign his name, in blood. Then a few weeks later, the guard would bring him his little bit of luxury. He had been delivered some extra soft pillows, a few more blankets, a pair of bunny slippers, a full-length mirror, several books, and a reading chair. He had also ordered subscriptions to The Daily Prophet, The Quibbler, and Playwizard Magazine. That last one was the most expensive of the lot. One guard, who had the Patronus of a camel but never gave a name, quickly became his primary supplier and sealed Sirius's loyalty by occasionally sneaking him in little freebies like beef jerky or strawberries.

Sirius nicknamed him Humpty.

Sirius had been noticing changes in himself since his murder spree began but had ignored them until now. One night, as he headed out for a kill, he looked in the mirror and noticed that Padfoot's eyes glowed red. The changes he had seen already were that his form was getting larger and teeth were getting sharper, and no amount of fasting would stop it. Regardless of the growth, he could still slip through the bars just as easily as before. He moved silently and didn't make any noise unless he wanted to. His fur was also messier; he had chuckled slightly as it reminded him of James' messy mop of hair. If Harry was lucky enough, he would inherit his mother's hair which was perfect all the time without brushing.

Now, seeing the eyes change to an unnatural and glowing red, he knew that it was more than just a bit abnormal.