Disclaimer: I do not own any (aside from a few originals in later chapters) of these characters. Their creation and fate is in the hands of JK Rowling.
Observe the Incomprehensible
It was all seen and heard from the Gryffindor tower.
The fifty one year old transfiguration teacher stormed out into the frosty grounds without so much as a glance at the equally frustrated person blasting from the castle behind her. Dumbledore had always said that magic leaves traces that an accomplished wizard can detect. The scene before the twelve students of Gryffindor who had stayed behind for the Christmas holidays, gave them a hint of what he was referring to. Although no magic had yet been conducted, even the students who were not by the windows could sense that something was happening. Each of the students, save a few first years who had not been around magic for long, felt an unusual tingle crawl up their backs making them twitch suddenly, all becoming uncomfortably straight-backed. Some kind of terrific energy from outside seemed to be invading their common room, and as curious glances were exchanged, people of the different years bewilderingly made their way to the windows facing the grounds of Hogwarts below.
Neither of the two figures below were running, and though both were walking speedily it appeared as though there was no desperate rush, as there seemed to be no destination.
"Professor McGonagall." The voice of Albus Dumbledore, louder than usual, sailed up to the high tower and met the ears of each curious student. They watched on as their transfiguration professor stopped short, her hands clenched into tight fists by her side - one, the students narrowly saw, was clasped tightly around a wand.
The Headmaster advanced defiantly in the direction of his deputy as she, like a flash, turned to face the figure striding ever closer. He stopped about four metres from her. A tremendous silence had fallen in the common room as each student strained to catch the words emerging from their professors' lips. As intently as they listened however, it was only the transfiguration professor's words they heard; from their headmaster all that reached their ears was a deep rumble.
"You are being completely unreasonable," Professor McGonagall barked in response to the low rumble heard from the Headmaster; her body was visibly tense and seeming to be in desperate need of bursting. The low rumble was heard once again.
"I will not go along with this, Albus," snapped the professor sharply, thrusting her wand back into her pocket. An odd thing to do, the students thought, though maybe she does not trust herself to hold back from cursing him if it is there in her hand.
"You will do as I order you to, Professor," thundered Dumbledore, his voice suddenly clearly audible to the students listening attentively as its volume rose with his anger.
"How dare you," spat Professor McGonagall in a dangerously low but phenomenally forceful voice.
"Look at the ground," one of the third year Gryffindors called out, astonished.
Each and every eye of the Gryffindor students lowered to the ground their two professors were standing on, and all widened in amazement. A glow was emerging from the surface of the grass and lay like a thick blanket of gently swirling, sparkling, golden particles between and around Professor Dumbledore and Professor McGonagall.
"Find another way, Dumbledore," continued Professor McGonagall in the same furious tone.
As the argument persisted, the momentum of the swirling glow increased and its mass grew bigger and brighter, like billowing smoke in an escalating blaze.
"There is no other way," Dumbledore fumed.
An awful vibration suddenly began making the air itself tremble around the couple in the grounds. The ever increasing glowing mass was now swirling vigorously as high as their knees and had begun to circle their robes causing the material to rustle as if caught up in a current of air.
"Don't say that!" Professor McGonagall replied with rage. "There is always another way!"
The fast motion of the glow continued, and then, all of a sudden, the students saw it split itself in half in the middle of their two teachers. One half began rapidly drawing a swirling ring of light around Dumbledore, and the other, mimicking it, circled Professor McGonagall, its high-speed spinning glow surrounding her.
"Why can't you understand that that simply is not the case here?" Dumbledore boomed back.
None of the students had any clue as to what was happening or about to happen, and continued to watch as their two professors stood in the grounds each now within a tube of spinning light, possibly as much as two metres in width, now reaching their mid-thigh. It seemed however, judging by the taut expressions on their professor's faces, which were now entirely visible because of the light encircling them, that neither was perturbed by the seemingly random appearance of these now separately glowing and fast- whirling energy fields.
"Because there is another way," retorted Professor McGonagall, and as all her emphatic frustration was forced into that one tiny middle word, the golden swirls burst into red lightning-like streaks, spinning faster and faster, encompassing her up to her waste. The students in the tower could now hear a sharp hum that had arisen together with the red streaks around their professor.
"I will not go through this with you again, Minerva." Dumbledore's angry warning exploded through the grounds but his circle kept its silent golden glow.
"You don't have choice," Professor McGonagall snapped back. "I will not accept your - totally irrational decision."
"You have to accept it," Dumbledore bellowed, this time causing his own golden, spiralling circle to flare into the same kind of red streaks that appeared opposite him, and the persistent hum, now doubled, echoed unpleasantly around the grounds.
The students were not sure whose circle was broken first. The red streaks from both professors cut themselves loose and ear-splittingly zoomed towards each other in a fierce ball of red light, full of the utter frustration and fury and passion that had been the initial cause of them.
As the energies collided with each other nothing exploded as the watching students anticipated, but the balls merged into each other at an equal and enormous speed, to become a single violently shuddering globe. As soon as the collision occurred, the globe seemed to compress into itself, causing it to rapidly and forcefully shrink in size. All of this happened in mere milliseconds, and as the limit of compression struck, the globe gave off a dull, but powerful, deep thud. So powerful in fact that you could see the ring of the shockwave it emitted, half a metre thick, speeding through the air like a huge wave of dimpled water, as transparent as glass, continuing in its ring but moving like lightning, ever outward, in midair.
The professors barely kept their control as the wave hit them full force in the chest. Their feet were ferociously wrenched from the solid ground beneath them and they were propelled backwards into the air, startling the students. As the teachers were hurled backwards both managed to stay upright in the air, and as they lost momentum they were able to gain some control. They landed, tumbling backwards but still on their feet, having been thrown over fifty metres from their original spot.
The shockwave dissipated as it ran out of energy and faded to nothing. Both professors, one hundred metres apart, still keenly (albeit unknown to either professor) watched from above, bent forwards and rested their hands above their knees as they gasped for air. The shockwave had been an extremely powerful one and it was evident that both were struggling to control their breathing. The thump to the chest knocked the wind out of them.
It was obvious to the students that this display was never supposed to go as far as it had, and it was clear that they had just witnessed a rare and extreme category of most potent magic. Their professors would never willingly demonstrate their feelings to this degree. It was well-known among the students and the magical community in general, that due to the risks of uncontrolled, and therefore wild magic, it is necessary for witches and wizards, particularly the more powerful ones, to learn to always control their more fierce emotions and therefore, more importantly, their powers. This knowledge encouraged the Gryffindors currently observing the events outside their tower, to assume that whatever the argument was about, it was a topic that, because of their professors' firmly fixed and evidently opposing points of view, had caused their frustration to boil out of their control and it had escaped from their normally unyielding grasp.
The grounds were now cloaked in a bright turquoise glow from a ball the size of a snitch suspended about four feet from the ground, emanating a lot of light for its size; the red light had vanished as the shockwave was released. Professor McGonagall looked up first and glared at her colleague who looked up a few seconds later and stared back. Both, still with shallow breathing walked slowly towards each other. Ever since the shockwave burned itself out, the energy of powerful magic in the air could no longer be felt by the students, although now, that was not what held them fast to the windows; it was their anticipation of what was to come.