[quote=LostBrotherGrimm]
Toss them out!
[/quote]

First... 

 Following the initial discovery of arrancars x amount of years(or centuries) ago, the twelfth division took an special interest in the research of the evolution of hollows. Exploring not just how they evolved, but also what factors led to certain evolutions, and the origins of hollows as an whole. It was during the process of investigating the latter, the specie's origin, that an 'new' type of hollow was discovered. One that had never evolved. This 'Alpha hollow' (pending better name) was theorized to be prehistoric, and was even believed by some to be the source of all hollows.

Thus, beneath the shadows of secrecy, the shinigami sought out this ancient being. Hoping it would be the key to eradicating the hollow plague once and for all. It was only following their success that they realized just how mistaken they were. As denizens of the soul society start to vanish by the troves, it soon becomes clear why this predator had never sought to change its form.

-

In a nutshell, they unearth an parasite-like hollow that is capable of infecting its prey with a venom that lingers in the infected, then repurposes their physical body functions after death. Morphing them into hive mind beings that seek to infect, then kill healthy beings as an means of spreading its influence. 

The idea being that this would be an universal threat, opening up the possibility for players to introduce non-shinigami characters and/or frequently explore all relevant worlds. Hence why I intended it to be a sequel arc. 

------

Second...

It happened suddenly. In one instantaneous flash, humanity vanished. Disappeared entirely. Homes, streets, even cloths lay empty scattered across the globe with their owners absent. Missing with no trace to be found. 

It wasn't twenty-four hours later that the soul society received a massage. An ransom. Humanity's safe return, in exchange for their surrender, and their lives. Left with an unanswerable ultimatum, the reapers were parylized by indecision. Their society standing at the edge of collapse as they sought to fight among themselves in question of the right response. Then she arrived.

According to her, they called themselves the (name). Featureless beings as white as snow. When she inquired as to their answer, they threatened to cut her down. She threatened to wipe them out. And so waged the first battle. With her defeat, and her capture, they learned the truth. Learned of their world, a place once deemed to dangerous to ever attempt to reach. A place the shinigami would now wage a war. Hoping to save save not just themselves, but also humanity from a foe they knew little about.

-

This one is simple, but can be built into something complex. New race, new abilities, new world. Possibility for human (and fullbringers) as well as quincies to be tossed in.

Thoughts?