Again, unedited/proof read because I just want to make sure it's not only on my computer when it dies it's immenent and inevitable death. Thanks for reading.
The battle had resumed by the time they returned to Hogwarts; Hermione apparated them into the entrance hall, right into the middle of a battle between a death eater and Luna Lovegood.
Grindelwald tackled them both to one side as soon as they materialised, narrowly dodging a curse from the death eater. Fortunately the distraction was enough that Luna's Pumpkin Head jinx scored a direct hit and it was then relatively easy for Hermione to disarm and stun him. The Ravenclaw witch smiled at them with her usually dreamy expression, taking the wizard beside her well within her stride.
'Gellert Grindelwald, I didn't think I would meet you, can't say I really wanted to though.' She said airily before announcing that she'd last seen Harry in the courtyard. She drifted off in the direction of the nearest group of battling students without so much as a second glance.
The Dark Wizard in question quickly retrieved the stunned death eater's wand and followed her as they wordlessly hurried in the direction of the courtyard. They took cover behind the pendulum of the clock tower to assess the situation. Harry and Ron were duelling Bellatrix, Ginny was teaming up with Neville to fight the Malfoys, McGonagall duelled two less recognisable death eaters at once.
They couldn't see Voldemort from their position, but Grindelwald didn't seem to mind. He fired off a couple of spells at McGonagalls opponents, then inspected his new wand critically.
'It is good to feel magic again, Miss Granger,' He informed her, 'but this wand is Shize.'
Then he tapped his throat with his wand and stepped out into the middle of the battle.
'You are a coward, Lord Voldemort.' Grindelwald's magically amplified voice boomed across the castle grounds. 'You claim to be the greatest Dark Wizard of all time, yet you couldn't face Albus Dumbledore in honest combat.'
Everything had stopped, every duel paused as both sides listened to the new unknown party. She could tell those that recognised him from those that did not; McGonagall whimpered and held her hand to her chest. A death eater with a bleeding nose from his duel with Kingsley hurled a curse towards Grindelwald. It splashed harmlessly against his shield and the Dark Wizard's wand flicked out so quickly that it was a blur. The death eater disintegrated into ashes without a sound.
With the death eater's distracted, Hermione waved frantically at Harry and Ron. They noticed her after several minutes and edged around the courtyard towards her.
'Hermione! We had no idea where you went. What happened?' Harry breathed as he slipped in behind the pendulum.
'Who's that?' Ron whispered at the same time.
'That's Grindelwald.' She continued before Ron could interrupt. 'He was furious when I told him that Voldemort assassinated Dumbledore – remember they were good friends at one point. Anyway, he agreed to help us defeat Voldemort.'
'That's Grindelwald? Isn't he meant to be like, over a hundred?' Ron seemed slightly confused but Hermione had felt his magic and had seen the distinctive eyes.
'I don't know, it's definitely him though. He swore his wand to me.' Harry didn't understand the significance of that but she could see Ron at least had some inkling. It was an ancient oath from back when people would swear themselves to a monarch, it meant that Hermione had complete control over Grindelwald's magic. She had the power to literally tear away his core if he failed to obey her orders. It was a lot of control to give to someone. Even now she could feel his magic through the bond, she could feel how he was tiring, how out of practice he was.
'We need to evacuate everyone. He's just providing a distraction so that we can all get away. Get everyone to Grimmauld Place' She told her two friends, they both nodded and Harry headed off to explain to McGonagall. Ron left to speak to Kingsley.
Hermione slowly began to crawl towards Grindelwald, he would need her to apparate him to the safe place as soon as everyone got away.
Spells splashed against his shields, his borrowed wand flared and flickered, spitting white fire at anyone in a black cloak. Hermione cast her own shield and jogged out towards him, fortunately most of the death eaters were distracted by the much more powerful wizard that was bottle necking the bridge.
He must have been aware that she was close because she was able to slip through his shields and into the protected bubble inside. He grunted out instructions with barely a pause and she willingly took over the left side of the bridge. It turned out that they were a terrible team. It was all very well at the edges of the bridge but they kept wasting spells on the same foes in the middle.
Meanwhile, Hermione tended to aim to disable, creating a maze of incapacitated foes for her opponents to try and climb around. The majority of Grindelwald's victims disintegrated, which created a path of least resistance to his side.
Grindelwald's powerful shield flickered, and Hermione quickly added her own underneath. They needed to get out of here but she had yet to receive any message from either of her two friends. She cast her patronus, Gridelwald hurrying to cover her as she relayed a message for it to deliver. The silver otter swam off and she was able to refocus her remaining energy on the shield.
Grindelwald was down to minor jinxes and hexes now. Bee stings, sticking shoes, tickling jinx. Sweat trickled down both of their faces. The death eaters were still fresh though as they freed their stuck comrades and rennervated those that had been stunned. Harry's stag appeared just as Hermione's shield failed, only managing to deliver half its message before a killing curse dissolved it into silver wisps.
Grindelwald dragged her into the cover of a fallen column.
'Get us out of here.' He ordered. She hadn't received anything from Ron but they had no choice, it was leave now or they would die. She grasped his arm and they disapparated with a sharp crack.