A/N: This is a demon!harry story, I don't know if this has been done, I've never seen one myself. Many of the demons themselves are heavily influenced by the daemons from Warhammer and Warhammer 40,000, right down to their names, while others were created in a similar vein by myself
Disclaimer: I don't own Harry Potter, Warhammer or anything to do with either
Harry howled in rage and despair as Sirius flew into the veil of death, slumping to his knees in front of the veil itself, his eyes falling closed as agony wrenched through his very soul, the very veil itself glowing for a few seconds as it took the young boy's godfather from him, stealing the fun loving marauder from this world into the warp beyond.
Harry's agony, despair and rage radiated from him, crashing into the veil as a wall of pure emotion, in our reality only for a few seconds, yet in the warp this was millennia, the portal between the two worlds, the Eye of Terror absorbing such raw and unbridled chaotic emotions, harnessing them and bringing the attention of the beings within the Warp itself. The Warp contained many creatures, beasts which had torn into our reality and many times wrecked chaos across time and space. Humanity knew them only as 'demons'.
These demons answered to one of the five great gods of chaos, Khorne, Tzeentch, Slannesh, Nurgle and Melkirth, beings of great power and true evil, and one by one they were alerted to the emotions being absorbed by the eye of terror. Rarely did the five great and powerful gods of chaos meet and even rarer did they agree to a truce, but with such powerful emotions so near to the Eye this was an opportunity they could not afford to miss, for this was the first chance in many billions of years for them to escape from the warp, and assault the world with their demonic armies.
Together the five mighty gods stood by the hole in dimensions, allowing Harry's emotions, his raw magical power, to wash over them, charging their own chaos magical power as the emotions of all mortals did. Slowly Tzeentch, a majestically bizarre monster who looked part man, part vulture, covered in iridescent scales and wearing flowing robes turned his avian looking head towards his fellow gods, speaking quietly, his voice a whisper yet it reverberated around the warp.
"There will be no truce once we escape to the mortal world, if any of you get in my way I shall kill you myself", his voice a whispering hiss, each of the chaos gods nodding in understanding, for none would be foolish enough to trust any of the others, least of all Tzeentch, the master of manipulation. Slannesh, the second youngest god, whose birth opened the Eye of Terror, a feminine creature whose seductive body was at contrast with her grotesque claws and lightning speed was the first to speak.
"Well, are we going to enter the mortal world now or not?" seeing Tzeentch's avian glare, and returning it. Melkirth, the very youngest and most human in appearance of the great gods the only differences being his size which he controlled with a mere thought and the large black feathered wings growing from his shoulders, chose this moment to barge straight past the avian and feminine gods and into the Eye of Terror itself, roaring as he was pulled out of the veil of death, appearing as a wraith to the battling mortals before vanishing into nothingness, three more wraiths appearing and vanishing as Nurgle, Tzeentch and Slannesh followed him, before the largest wraith exploded into existence, Khorne surveying the battlefield, swooping through Harry's prone form and vanishing like his fellow gods.
Harry screamed as the wraith flew through him, the moment it vanished his eyes turning red, lifting his wand towards Bellatrix, the sound of a cannon reverberating around the room as she flew into the wall, hitting the stone with a sickening crunch, falling down to the ground like a rag doll, bones sticking through her flesh.
Harry could see Neville staring at him in shock but didn't give it a moment's thought, eyes turning to Ron as the redhead groaned, looking over at Bellatrix then back at Harry, whispering his almost trademark
"Bloody hell mate" before glaring at Harry for a second the moment his 'friend' looked away, muttering to himself "He gets all the fame, glory, now he has stupid amounts of power too the lucky bastard, how come he gets to be famous while I get nothi-" being cut off as a stray stunner blasted the jealous redhead into a wall.
Harry snarled as he stepped into the atrium, able to hear the battle behind him come to a conclusion. He could sense a dark presence looming in this room, not like the wraiths from before, this one was mortal, leaping to the side the exact moment a green blot of light hit the ground where he had been standing, able to see Voldermort standing on top of the centaur in the fountain.
"Mr Potter, what a surprise to see you here" the dark lord drawled, almost lazily flicking his want, another Killing curse sailing at Harry who promptly dodged, returning fire with a blast of magical flame from his wand. Harry had no clue how he was casting these spells, especially non-verbally, he just could, the black fire hitting Voldermort and smashing him back against the wall.
Seconds later Harry found himself falling to the floor in a full body bind cast on him from behind, eyes turning enough to see Dumbledore step past in his horribly bright robes with a self righteous air around himself, speaking casually, pompously and arrogantly
"I'm sorry Harry my boy but I can't allow you to endanger yourself fighting Voldermort, I shall do so myself", turning to Voldermort and lifting his wand, only for a red spell from the Dark Lord to smash him into the fountain, the old bearded mage coughing and choking for breath as the Dark Lord advanced on him.
Fortunately for the wizened old fool seconds later the fireplaces began to spit aurors and the minister of magic himself out, Voldermort finding himself with over fifty wands pointed towards him and wisely apperating away instantly. Dumbledore groaned, slowly pulling himself to his feet as a shadow slid through the water, enveloping the old man for a few seconds before dissipating, Tzeentch smirking as he inhabited this manipulative vessel, inhabiting yet not controlling the body.
"That was Voldermort, he's back…" whispered Fudge from across the atrium, Dumbledore straightening and aiming his wand at the aurors, roaring "OBLIVIATE!" before swooping over, grabbing Harry and apperating back to his study
"How?" Harry practically snarled as he sat shaking with rage in front of Dumbledore's desk, his eyes toned on the old man standing in front of him.
"It was for the greater good" Dumbledore proclaimed grandly, settling himself back behind his desk and seemingly ignoring the irate Chosen One sitting the other side.
"THE GREATER GOOD!" Harry roared, his green eyes burning with a deadly fire before turning a blood red, his mind flashing back to when Dumbledore had obliviated the minister of magic and the aurors not an hour ago "YOU LET THEM GO 'FOR THE GREATER GOOD! I COULD HAVE KILLED HIM THEN!". With that Harry's entire body was engulfed in a black fire, his voice distorted and daemonic causing the old fool Dumbledore's head to snap round and his wizened hand to reach for his wand "You have no idea Dumbledore, no clue what they unleashed".
For once Albus Dumbledore had nothing to say, just watching, mouth agape as Harry stood, hand moving to the wooden desk and tossing it easily away into a wall, the inhabitants of the paintings scampering away in terror as Harry advanced on Dumbledore.
The old goat finally realizing the danger he was in managed to mumble out, "Expelliarmus", Harry's wand flying into the older wizard's hand but Harry's demonic flames not vanishing for a second, the teenager's eyes filled with pure malice, Dumbledore mumbling out "Stupefy", the red spell shooting forwards and dissipating as it reached it's target.
Harry gave a dark chuckle and an evil grin, showing off long glistening canines, appearing to have gained at least two feet in height, smirking as Dumbledore cast a shield charm and Harry shattered it on touch, Dumbledore's eyes doubling in size before he shouted out;
"Imperio!" Harry freezing before roaring with hellish laughter, hand shooting out and fingers wrapping around Albus Dumbledore's wizened throat, lifting him into the air. In a strangled tone Dumbledore managed to whisper "Avarda-" before being cut off as Harry's finger closed around his wind pipe, Harry's other hand lifting and shooting forwards, smashing through Dumbledore's rib cage, fingers wrapping around the old wizard's still beating heart.
"Don't worry Albus, you'll have company in hell soon" Harry growled, ignoring Dumbledore's groans and whimpers of pain, squeezed, crushing Dumbledore's heart to a bloody pulp in his bare hand, a dark shadow dropping silently from Dumbledore's body through the floor as Tzeentch made his escape from his now dead vessel.
Harry dropped the corpse with a hiss, kicking it across the room where it hit the stone wall with a sickening crunch, Harry's lips curling up to expose his fangs once again as he felt his body beginning to change. Within seconds he was a towering, muscular behemoth, his face bestial and almost canine, a huge bloody maw filled with incredibly deadly looking teeth and with sharp horns adorning his head. He was clad in the brass armour. Most noteworthy were the great leathery wings that burst from his shoulders, the entire ensemble finished by the strange eight pointed star symbol which now sat on Harry's forehead.
Slowly demon-Harry turned to the door, his eyes glowing red for a second before the doors exploded off their hinges, burning as the tumbled down the spiral staircase away from him.
Demon Harry growled softly as he slid across the damp grass towards the Hogwarts gates, it was still night, and he had managed to swoop down from Dumbledore's office to the ground instead of having the fight his way through the castle.
Harry's mind was screaming, trapped inside his head, his rage at the ex-headmaster allowed one of Khorne's demon servants to take full control of his body, forced to watch as the demon murdered his headmaster, trapped within his own head as the Bloodthirster demon stomped towards the forbidden forest, hearing the scream from the castle but unable to force the demon to turn and look, force the beast to stop it's march into the forest
A prisoner to the demon