Ever since Emma has come to town, Regina has been spending her nights reading and re-reading ever magic book she brought with her.
She has developed multiple plans to contain the sheriff. All of which had failed.
The first plan that came to Regina's mind was to simply take Emma's heart while she slept. That would be also be a fine replacement to Graham. This would give her a pawn that can do her bidding. Oh how she would have loved that plan to work. But there was one loophole. Emma's heart was protected with true love's magic.
She had discovered this with a simple sleeping potion she put in Emma's drink on the first night she was in storybrooke. She felt the danger of a stranger in town, and this was supposed to make her sleep by the second sip. But she finished the drink like a shot and went on her way.
She had limited magic she brought from the fairytale world, so she had to use it wisely. She couldn't go around trying random methods without a plan.
She tried to use others to do the job. Graham and Gold. Mary Margret and David. Even Henry. But nothing worked. Emma would undo her work as if by fate. Every. Time.
So she hit the books. Even though she knew her research was pointless.
It was the basics of magic. True love is the strongest magic and that's what Emma had to overcome the sleeping potion. But she couldn't give up yet. Her perfect world depended on finding a way and she couldn't let it go.
Today she finally found... or re-found the spell that would help her. It was Henry who gave her the idea. He was writing his homework as she cooked dinner for them. She had lost herself in a deep well of fear. She feared that she has failed again. That there was no way to stop Emma and suddenly Henry interrupted her and said "Emma will always win." She looked in his eyes and saw that he knew she was coming up with a plan to stop his birth mother "if it's a fight, good will always win"
"You should stop reading that delusional book of yours." She tried to pretend everything was normal "I'll get you a real grownup book tomorrow." After eating, Regina sent Henry to his room but his words echoed in her mind. "If it's a fight."
As soon as she heard that line, a new plan instantly clicked in her head. Her son, like her, had been hitting the books. He had excellent knowledge of the lure of the storybook, but unknowingly to him with those words, he became her saviour.
She waited till he had slept, and then she went to the tomb where her secrets were kept. Her plan was simple. She gripped her magical diary. Her "book of shadows" and flipped to the first page.