Thornblood, formerly known as Lavender Brown, crept out of the Forbidden Forest the night after she saw Rose Granger-Weasley and then prowled around Hogwarts while planning her next move. As she was planning how she will take out her vengeance, she remembered the Snatcher that mauled her during the Battle of Hogwarts. She knew that in order for her plans to work, she would need help. As she lurked upon the school grounds undetected, she learned the identity of the one who almost killed her; Fenrir Greyback. He was the one who infected her and he was the one who destroyed any chance of winning Ron's heart while still a student. He also was the main leader of the Snatchers who served the Death Eaters. As the result of Lavender not being attacked on a full moon, she had to feed on a human on a full moon to actually become a werewolf which means even if Thornblood were to kill Greyback, she would not be able to cure herself of her lycanthropy. She would however gain the respect, fear, and loyalty of the remaining Snatchers and use that to her advantage. With this knowledge, she set off to take care of unfinished business.
As Thornblood studied the Dark Arts intensely in order to more easily take out the scattered Death Eaters that remained after Voldemort's death, she went looking for Greyback. She eventually found him in an old abandoned flat laying down on a dirty and torn bed. She used her wand to catch him off guard and drag him on the floor and then demanded him to tell her where the remaining Death Eaters and Snatchers were. "I'm not going to ask you again. WHERE ARE THEY?!", Thornblood demanded again. "You think you can make me tell you? Please." said Greyback sarcastically. "You know how many witches and wizards I killed?" he added. He then took a closer look at her eyes and smelled her scent.. "It can't be... Lavender? I thought I killed you!" said Greyback. "No, you stupid oaf. I killed Lavender! It's because of you that she's dead!" replied Thornblood. "Lavender was weak and I'm going to be everything she wasn't. Now tell me, where are they?" she asked again. "I'm not telling you." replied Greyback smugly. "Crucio!" shouted Thornblood. Being able to endure the curse only so long, Greyback replied that they were all hiding in a town near London as fugitives from the Ministry of Magic. "Thank you. Now there's one other reason I came here... Avada Kedavra!"
Now that Fenrir Greyback was dead, Thornblood goes on her next mission to wipe out every single Death Eater and recruit every remaining Snatcher and kill those who refuse to join. She's on a mission for glory to show how far she would go to have Ron and to reveal the kind of hypocrisy the Ministry of Magic enforces. She's on a mission to create a new kind of Ministry; one that integrates muggles and magic folk alike. In order for that to happen, she goes on a journey to form a group among the Snatchers who unspokenly disagreed with Voldemort's ideals and who agree to help her hunt down and kill every witch and wizard from school to school who abides by the Ministry; teacher and student alike. She'll do whatever it takes to bring fairness to the world by giving muggles that believe in themselves a chance to become witches and wizards and also whatever it takes to prove to Ron how she's better for him in every way than Hermione. With this in her mind, she sets out to become the most powerful and respected witch anyone has ever seen.
And so Thornblood's story continues...