The Abigail Williams in this story is the same Abigail that appears in Fate/Grand Order's Salem chapter.

For those who haven't played Salem, this chapter has spoilers. You have been warned.

Some background. Abigail is a person born in a Sigularity, a distortion of human history. She became the host of the Outer God Sut-Typhon, but was eventually calmed down by Ritsuka Fujimaru, the main character of FGO. She left the Singularity with a person who only described himself as "the gentleman who travels through space and time." She is capable of being summoned as a Foreigner-class Servant, but only during irregular conditions.

This chapter is short, because I want to see how people feel about the idea before I start to spend time on it.

AHHH! ABIGAIL ISN'T LISTED IN THE CHARACTERS OF FATE!

Abigail Williams was far from what one could consider a "normal" Servant. She was just a side note in history, hardly capable of qualifying as a Heroic Spirit.

However, by forming a connection with the Outer God, Sut-Typhon, she was at least able to cement her existence as a Foreigner. Not one of the standard classes, but an extra class that few qualified for, as well as a spirit that was capable of acting without a source of prana, seeing as she could generate her prana by herself.

Of course, there were benefits to contracting with Sut-Typhon. As Sut-Typhon was the god that was both the Key and the Gate, the All-In-One and One-In-All, Abigail could traverse space and time. She found herself wandering through the dimensions, opening gates to her next great journey wherever she pleased.

She hadn't always possessed such control over her abilities, though, and had to thank Carter for that. Carter had been a kind gentleman who traveled through space and time. The two had gone their separate ways after Carter had finished teaching her, both agreeing that it would be good for Abigail for her to experience life for herself.

After leaving a world where the where someone had created a park full of dinosaurs (silly idea, really, considering how dangerous such things could be), she visited a world where humanity was on the brink of extinction from creatures known as the Titans. She pushed a boy, Levi, in the right direction to become someone who would defend humanity from the Titans, trusting his stubbornness to get him enrolled as a member of the Survey Corps, before once again leaving. She briefly wondered if she should go see Ritsuka, before she chanced upon little Harry Potter.

She had only been planning on taking a peek before meeting up with Carter for her sort-of-annual (time traveled differently for her) checkup, and was immediately shocked when she was greeted by a vision of a little boy being whipped by a belt. Living in such conditions! Even if it was nothing new to her, who had seen worse situations in slave trades and other worlds, it still hurt to watch as the walrus of a man whipped the young boy for something as small as burning the eggs slightly.

Before becoming a Foreigner, Abigail had been been a faithful Puritan, and those teachings compelled her to help. Time was not an issue, as with the power of the Outer God, she could simply turn back the clock. Yet, she did not know if this was one of the worlds with magic. If the world did not have magic and she revealed herself, or if magic was a secret in this world, she could make the situation worse for the boy by appearing in front of his enraged uncle, who most certainly would not agree to keeping her appearance a secret.

However, if she waited until there was just the boy, then even if the boy told someone about her, it was unlikely he would be believed. So instead, she decided to wait for the boy to be sent to his cupboard under the stairs before acting. She could at least heal his injuries before her appointment with Carter to see how she was doing.

Harry Potter, only seven years old, was shocked when he found a young girl in his room. Well, "room" was stretching it, as it was merely a cupboard under the stairs.

Harry, who had been on his "bed"(actually, just some random things he had found) trying to read a book and forget the pain, noticed the girl standing by the closed door. She seemed to be older than him, if only by a few years. She wore a black dress with many frills and a small hat. Her head and her dress were adorned with bows. Her skin was pale and her hair was blonde. In her left arm, she clutched a teddy bear. On her face was a small frown.

But her most distinctive trait were her eyes. They were a bright azure color, but as Harry watched, flecks of purple occasionally swirled into view.

"W-who-"

The girl brought her finger up in a shushing gesture. "I'm Abigail," she whispered, stepping closer to the Harry. "Let me see your back."

Harry flinched. Not wanting to show the marks he had received from his uncle's belt and still somewhat shocked, he refused to budge as the girl stepped right in front of him.

The girl pushed him up as she moved to the side of his makeshift bed, ignoring his feeble protest. She shifted his shirt up, and Harry waited for her to say something. To his surprise, he felt the pain receding. Not wanting the girl to stop whatever she was doing, he continued to hold still.

Soon, the pain was gone, and the girl backed off. She was blushing slightly - Harry wondered why - but she smiled at him and murmured a short prayer.

"I'll be back," she said as she walked to the door. Harry's eyes widened in surprise as the doorway was replaced by a swirling black hole. "Don't tell anyone about me, ok?"

"W-wai-"

And with that, she was gone.