Disclaimer: I do not have any ownership of any character in this story. None at all. Not of the BtVS characters, not the ATS characters, and not the Characters from the Kate Daniels' novels.
Cracking the Seed.
Buffy swung the Scythe at the Seed. Too bad none of the Scoobies had paid that much attention in Biology class.
The world seemed to freeze for a moment, then the Seed disappeared. A heartbeat later, there was a flash of bright white light, and Willow was gone. She had been wide open to draw in magic for so long, to such an extent . . .
To this day, it is argued whether she combusted, or ascended to become a Goddess. Or to merge with a Goddess. If she Ascended, she has not answered any prayers or pleas.
Willow was always more concerned with computer classes, and with Chemistry and Physics. She took the basic biology classes, but never studied it to the in-depth feature of the other sciences.
Dawn was the next to vanish. Of course, in her case, it was in a flash of bright green light. Well, she didn't completely vanish. In her place was a small glowing green orb-shape. Xander broke down almost immediately. It took him months to regain his mind. Eventually, he was instrumental in forming an Order of Knighthood, to help others.
Dawn had never had the opportunity to study biology to the extent needed. Xander, of course, slept through the class; he counted on Willow to give him the information he needed.
Buffy, and the rest of the Slayers, barely had a chance to move, before the Demon-energy infusing them reacted. Each had a different causative reaction, but the end result was the same. Their essences were all twisted, changing them. Some were twisted on the surface, becoming Were's of one sort or another. Others, even worse, were twisted internally, becoming monsters, though of a more human kind.
Buffy, as the oldest, became hardened, as she had tried to harden her heart, her skin now tougher than stone. And about as mobile. Faith, the last true slayer, suffered the worst fate, as the Demon they all got their powers from ate her from the inside out. It was not a fast process. She was able to protect Xander for long enough to get him away from the others, before she could no longer take the pain.
Buffy had never taken Biology, after the loss of her favourite teacher sophomore year. She just couldn't hold any pleasure in the study. Faith, the street child, never took any Biology at all.
Spike, the younger of the two Vampires, was less affected. His fangs grew uncontrollably, and his spine started a hunching shape. His arms and legs both lengthened slightly, as his pelvis altered shape.
Angel, being over a hundred years older, was worse. Due to his age, his body lost the ability to walk upright, as the hunching of the back, and the alteration of the pelvis was nearly complete.
In both of them, the demon that was inside grew incredibly in strength. Only the fact they retained their souls, long after the bodies should have been dust allowed them to retain their minds.
Angel had been a bootless lad, and ignorant. He knew nothing of the Biology of plants, having avoided the subject. It had, after all, been near and dear to his land-owning father's heart, and thus anethema to the young Liam.
Spike had been more focused on his poetry, on his words, than on any of the sciences. He had no idea what was going to happen.
All across the world, those of any little bit of demon blood felt the effects. For most it brought the Demon portion to the forefront. For some, it enhanced gifts, to powerful extents.
Vampires, those without souls, instantly lost all intelligence. The older they were, the faster they lost the semblences of humanity. Some few humans, very few, gained an uncanny gift to control the now mindless beasts.
For the Were's that already existed, in the weakened magic of the before time, it brought both blessing and curse. Their gained the ability to retain their minds while fully Were'd out, and the ability to Were at will. It also, however, brought greater requirement to control the animal, to balance, or the beast portion would go Loup.
In a small cavern, in Iraq, an ancient Sorceror, old before the last fall of magic, felt the wave. He gloried as he regained what had been diminished. He began to make plans immediately. "I always like the name Roland."
His sister, older but wilder, than him, felt the power as it washed over her in the bar she was in. Her killing spree destroyed a town; there was not a single survivor.
As people began to change, as hidden long lost aspects regained power, technology seemed to fail. Any building taller than 50 stories began to have problems. Most fell, toppling and killing thousands. Cars failed to work. TV's still worked, but the satellites failed. Telephones were intermittent at best.
It would be known in the future as the Three Week Riots. Millions were killed, both normal and magical. It brought new challenges, new opportunities, and new threats.
What none of the Scoobies seemed to realize was that some seeds needed an outside force to activate them. Some needed to pass through an animal's digestion system. Others, like pine cones, needed to be burned. And some few had to be cracked open.