Half an hour passed far too quickly and an expectant hush fell across the room as Grindelwald stepped back up to the platform. He counted down from five, then tapped his port key with his wand. Hermione felt a sharp tugging at her navel and the world compressed around her, spitting her out again in an empty field. She felt the hum in the air as McGonagall and her two student volunteers raised the anti apparition jinx over the whole field. Grindelwald stood out at the front of their force, they could see Slughorn across the field from them at the head of his group of students but Kingsley wasn't visible, indicating that the warded house was somewhere between them.
For a couple of seconds there was silence, then Slughorn's students let out a colossal roar, launching a volley of potions into the air. The glass vials shattered against the wards; fire, ice, acid and a smoking violet concoction splattered like paint across the invisible dome. From the south west came several bangs and pops and the echo of young voices shouting different spells. Then their group in the north launched their first attack, powerful spells blasting across the mirage, lighting the dome up white and showing the exact outline of the protective shield.
For a second there was silence, then another volley soared across the space between them. Slughorn's students were screaming battlecries as the lobbed potion after potion at the ward, painting their side in an array of bright colours. Hermione cast stunner after stunner, on her left Harry was doing the same and on her right, purple curses flew from Grindelwald's wand. Flitwick was using something yellow, George was setting up a volley of fireworks and Molly Weasley was screaming something about Fred's head. Whatever curse "Fred's head" was seemed to be doing considerable damage, almost as much as Grindelwald's purple curse, which lit the entire shield up white every time it impacted.
Then, booming over the sound of the spells, slithering deep into the darkest parts of her soul and leaving Hermione feeling sullied, Voldemort's voice whispered over the battlefield.
'You are fools, you believed that we were unarmed. Now you will face the consequences of your actions.' The barrier suddenly became transparent, the mirage of the field wavering and disappearing. Horrified screams rent the air, for between them and the cottage, pressed up against the barriers, waited an army of inferi. The horrifying bit was that they were of all ages – children dressed in tattered Hogwarts robes, parents and grandparents. Voldemort had raised the dead from the battle of Hogwarts and sent them out to fight against their living friends and families.
The corpse that led them though was unmistakable despite having been dead for over a year; his long white hair and beard, his robes still pristine as they had been when he was buried. Albus Dumbledore faced them across the space.
In the field of shock and horrified despair, a supernova exploded next to her. Grindelwald unleashed a storm of darkness which swept across the field almost tangible and crackling with power. Then suddenly it sucked in before he screamed an incantation that was lost to the roar of white lightning that shot from his wand.
The bolt hit the shield with a clap of thunder and the warding split open as if it were an egg. Gellert sliced his wand horizontally across the field, blue fire streaming from his wand and blazing into animal forms. It seared a ring around the house, hugging its master as he strode through the fire. The army of inferi rambled forwards, unaware or uncaring as their comrades were vaporised by the blue fire. Grindelwald advanced forwards; dragons, basilisks, thestrals and chimeras plunged around him, wings and tails whipping his foes into dust.
Voldemort's undead army was decimated within minutes before the fiendfyre converged on the body of the headmaster with the force of the bomb.
Death eaters appeared around the edges of the field in swirls of black smoke, engaging order members in duels. With no cover the battlefield descended in chaos within seconds, crossfire taking out as many combatants as direct duelling. Harry and Hermione cast shield charms as they hurried across charred grass after Grindelwald. There was a massive explosion as he blew the front face off the cottage, dark magic still swirling around him with unimaginable power. The stone shards froze mid explosion, changing direction and knifing towards Grindelwald. He blew them to dust and sent another reductor curse into the front room of the cottage. A woman screamed from inside but Voldemort finally became visible. The two dark wizard's wands were a blur as they cast spells quicker than Hermione could see, jets of light shot into the crowd of combatants around the cottage, agonised screams proving that none of them were minor jinxes.
'We have to get a shield up around them!' Hermione screamed at Harry over the noise of the battle. The boy-who-lived jerked his head in a sharp nod. 'Cover me!' She shouted, beginning to erect a dome over the two duelling wizards. Harry deflected the scattered curses that came close to touching her as Hermione struggled to hold her shield. Every spell that hit it felt like a physical blow, reverberating into her bones.
Then suddenly it stopped.
An inhuman, tortured scream rent the air and Hermione spun to see Grindelwald, elder wand levelled at the younger dark wizard. Voldemort was on his knees, head tipped skyward and mouth opened to make that awful sound. A woman screamed, barrelling out of the building and throwing herself into the path of Grindelwald's curse.
As soon as she came between the two, the spell was broken. Grindelwald tossed her aside with a casual flick of the elder wand.
'You've got to end it Harry.' Hermione said urgently. Harry nodded and sprinted towards the two dark wizards. Bellatrix stood from where she'd been tossed and noticed Harry careening towards her. The dark witch raised her wand at the boy who lived but Gellert's training paid off and Hermione's tickling jinx sent her aim wide. Bellatrix turned to her with fury, slashing her wand diagonally. Hermione deflected the curse, then returned with a slicing hex, Bellatrix deflected it with a contemptuous flick of her wand.
'Is that all you've got, little girly? The Dark Lord himself has trained me!' she taunted, Hermione deflected a cruciatus and a sectumsempra with equally contemptuous ease.
'No.' Hermione gritted out. 'Gellert Grindelwald trained me.'
She let one of Bellatrix's curses splash against her shield, taking the opportunity to turn the ground beneath the other witch to slick black glass. Bellatrix slipped as she cast her next curse, which gave Hermione the chance to go on the offensive. She unleashed a barrage of hexes and jinxes, watching as Bellatrix's expression changed from amusement to concern and eventually shift to fear. The younger witch transfigured the ash into sand, whipped up a storm and battered the older witch. She sent several stunners towards the sandstorm, hoping they would be concealed by the dust. Bellatrix used a wave of power to blow the dust away, then dodged the stunners at the last minute. Hermione's fire spell singed the witch's wild hair, then little birds backed the witch straight into Hermione's final stunner. Breathing heavily, Hermione stood over her defeated opponent, thick ropes twirling out of her wand and binding her foe.
She looked up to see that the rest of the battlefield was in silence, watching as Grindelwald spoke to his defeated foe, his wand not wavering an inch.
'What's wrong.' She asked as soon as she got close.
'Something is wrong with him, Hermione.' Harry muttered to her. She looked closely at their dark friend. Harry was right, she realised. It was something in his posture, in the way his magic roared without any mercy or hesitation, maybe something in the set of his wand or the look in his eyes. Either way, Hermione realised that she was face to face with the Grindelwald that Dumbledore had described rather than the one she'd become friends with.
Tentatively she reached through her occulumency barriers to where their bond pulsed. She reached out for his magic, preparing herself to tear it away if he tried to attack her. Then she crept up to him.
He ignored her as she approached, which she took to be a good sign.
'Gellert?' She whispered. 'It's time to end this. This isn't right.'
'He dared to insult Albus' memory.' Grindelwald snarled, recasting his curse. Voldemort cried out soundlessly, his voice worn beyond use.
'Albus believed in mercy. Please, Gellert, lets finish this so that we can go home.' She begged. Grindelwald paused, his curse fading to leave the defeated dark lord whimpering.
'Would he not want me to avenge him?' He asked, sounding strangely unsure. Hermioen rested her hand on his arm.
'Not at the cost of yourself.' She whispered and Gellert took a shuddering step backwards, lowering his wand shakily.
Harry looked at Hermione, who nodded, leading Grindelwald backwards. She heard his soft spoken Avada behind her, knowing that it was an act of mercy and her friend's soul would remain undamaged.
She wrapped her hand around her port key and spoke the words that would take them home.