Every living sorceress in the entire land had been taught by Rumplestiltskin at one point or another. There was no way that you could become powerful enough to become a sorceress without some education given to you by The Dark One. Just like Viktor Frankenstein, Rumplestiltskin was in the business of making monsters, well, he wasn't in the business of it, so much as he enjoyed corrupting what others believed to be pure. He had taken all of Cora's hidden cruelty and greed, amplified them, and brought them out, subjecting everyone to faults that no one was even aware she had. He had turned the Blind Witch from an innocent baker's apprentice who loved children, to an insane cannibalistic hermit who loved eating children. He had turned Maleficent's best friend Regina from a gentle noblewoman to a power-hungry, selfish tyrant who would do anything to get what she wanted or to spite those who stood in her way. And he had turned Maleficent from a content farmer's daughter, to a bitter hag who transformed into a dragon, something even more horrific and loathsome than a werewolf. Rumplestiltskin had molded her like a piece of clay, destroying whom she had been and making her into something else entirely, changing her for the worse. He liked taking the hidden flaws that people had, and making them their defining qualities, and no one knew this better than Maleficent.
Maleficent had been content, she had been happy to be the simple, blissfully ignorant farmer's daughter. She had been so desperate for wealth and financial security that she had been willing to give up her happiness for it, but now she would trade ten years of bad harvests for a minute of happiness unadulterated by bitterness and the empty feeling in her heart that she felt at every moment. She had thought that her sacrifice of her happiness for her family's financial security had been altruistic, but really, it was selfish. Though they were poor, her family had been fulfilled, and she had taken that away from them just so that she could feed her greed and her ambition.
Rumplestiltskin had come one day, during a particularly bad harvest. Her family wasn't sure that they could make it through the winter. Her parents were considering selling the land, when the Dark One offered them a deal. Their harvests from then on would be bountiful enough to feed their entire starving village, if they would only agree to give up the thing they loved most, their only daughter. Maleficent's parents had had trouble conceiving, and it wasn't until they made a deal with the witch Cora, that they were able to have their one and only child. Despite the pain that they knew it would cause them, Maleficent's parents agreed to let Rumplestiltskin have her. They had always had a very utilitarian philosophy. So Maleficent left with Rumplestiltskin, and he molded her into the person he would eventually become.
He taught her black magic, corrupting her little by little. After about a decade of teaching Maleficent magic, he arranged a marriage between Maleficent and the king of a small land. She would marry him, and then after a year of marriage, she would use magic to kill her husband. She knew that Rumplestiltskin was just using her so that he could have a queen in his pocket, but she didn't care. She was so obsessed with having more power, she could never have enough, she was always hungry for more. Power had become her drug, and he knew that. He was using her addiction for his own devices, but she was such a junkie that the only thing that mattered was her next fix.
Maleficent infiltrated his court, and made sure that she seemed mysterious and unavailable. The king had a reputation for having a weakness for the ladies, so she knew her job wouldn't be hard. Within a month they were engaged. Maleficent's life was perfectly plush, everything was going completely according to plan, she had married the king, killed him and made it look like he'd just died of old age, and gotten complete control over her land and everyone in it. Yes, her plan was going completely smoothly, until she met the young prince Phillip. They started having an affair, and Maleficent started to fall in love with him. It was the first grain of happiness that Maleficent had experienced since before her lessons with Rumplestiltskin. she could have had happiness, but Aurora took it away from her.
Aurora found out that Maleficent had murdered her father and was having an affair with her boyfriend, so she blackmailed Maleficent into ending her affair with Phillip. Maleficent knew that her life and her career would end if she didn't give in to Aurora's demands, so she couldn't take the chance that Aurora wasn't bluffing. So she took matters into her own hands and cursed Aurora. She didn't want to kill her because she admired her deviousness and she wanted her to experience the living hell that was the sleeping curse. She cursed Aurora and moved her to a secluded temple in the middle of the forest. She was satisfied at the success of her curse, she would never have to deal with Aurora again, but she would never be happy again. She came back to Phillip to continue their affair, but he found out that she had cursed his girlfriend so he ended their affair and started a quest to find Aurora and save her. Maleficent thought that Phillip was being ridiculous, but she realized that she wouldn't be able to change his mind so she would have to move on. She told herself that she would never fall in love again, that she would devote all of her time to expanding her empire and becoming more powerful, both magically and as a queen. She got everything that she had ever wanted, she was living out her most far-fetched fantasies, but she couldn't help but wish that her life was simple again. She would trade her entire kingdom, if she could only have her farm back, if she could see her family again, if she could only have happiness again. She shook the thoughts out of her mind and ruled her kingdom with an iron fist. Sometimes, after she'd conquered an especially powerful kingdom, after she'd proven to everyone how powerful she was, she felt a little rush and she could trick herself into thinking that power was happiness.