Hermione knew she needs to be lethal and ruthless for her vengeance. However, her incomplete education at Hogwarts wouldn't help her anyway. Dark Arts and arcane fields of magic are the only ways, she can fulfill her vow, which is what led her perusing through Knockturn Alley for contraband study material. As she started reading up on them, realized that she had a knack of performing darker spells and had good control over them inspite of the wand not being hers. She needed a better wand, but that's for another time. Learning spells was all fine but practicing mind arts was something she found difficult due to a lack of practice subject. However, the opportunity soon presented itself as she found the tainted ex-minister drunk and slightly tipsy exiting the White Wyvern on a deserted night. It didn't take long for her to stun the portly old wizard and apparate back to her safe house, which was basically an abandoned acid factory at the very edge of muggle London. It still held many tanks with active, corrosive acids, over one of which hung the ex-minister.