The Scarlet king

Genesis

Somewhere in the infinite depths of the The Ethereal Plane exists a demiplane whose boundaries are filled entirely with something akin to blood. When or how it came to be? Even the gods do not know, for when they looked upon their world, it was already within its depths. Silent, stagnant and yet terrifying to them. Long before the current era of the world, a curious team of explorers of the deep ethereal stumbled upon it. The poor creatures never even understood what they had stumbled upon, as simply entering the demiplane spelled their end. The dimension's boundaries took everything from these poor souls, its eldritch existence melding with theirs; and since then the strange realm's mindless existence had been plagued with the thoughts of its victims. Fear, happiness, impatience, all of a sudden it could feel and think, concepts that previously weren't part of its existence. But of all it could suddenly feel, one desire stood out, a desperate wish to return to a home it never had, unconsciously driving it towards the one thought in common in its divided minds: the realm of Aurora.

The minds of the explorers in its depths unknowingly manifested strange abilities in their captor; the ability to anchor itself into those with strong, magical or otherwise unique bloodlines it had previously come in contact with. Due to this, through the blood of the expedition leader, it inadvertently began to influence those of his bloodline. A sort of earworm, thoughts both vague and everchanging started haunting the family of the explorer. Over the course of their lives these invasive thoughts and nightmares never waned, making them believe they had been cursed. Due to its sudden manifestation in an age of peace, its origins where completely unknown to them, and so they lived trying to disregard what was happening to them. One of them however simply couldn't ignore it, and spent years studying the half-thoughts and strange dreams that plagued him. He found a pattern within them, he was convinced his grandfather which had disappeared in the ethereal realm many decades ago was trying to call to him, begging to be saved from something...

Pupae

Over the next decades this man would study ethereal travel as well as conjuration magic for a way to reach the one he believed was calling to him. Slowly gaining insight after insight into the secrets of theses magics. Those around him who didn't know what was happening within his mind simply called him a prodigy. Thanks to this he gained the attention of powerful figures, and since they could offer him the ressources and funding he needed, he shared his findings with them in exchange for their support. However, he only shared superficial information and kept his studies in his journal under a cypher only he knew the key to. He feared what would happen if his patrons ever learned what his singular goal was.

Nexus

Thanks to this new backing he achieved breakthrough after breakthrough, until finally... he managed to create a spell that he believed could reach anyone or anything as long as blood or anything similar from its lineage was used as a part of the spellcasting; Zephyr's threshold. Aware of how powerful such a spell was and the risks it could incure if the wrong hands had access to it, he lied to his investors, claiming he had reached a bottleneck and his research was stagnating. Still, he needed their help to obtain all the required components to his new spell, so over the next year he came up with increasingly strange stories to explain why he needed the specific things he was requesting for his research. Subtlety not being his strong suit, his investors were aware he was hiding something from them, but curious as to the outcome of his machinations.

Paroxysm

Once everything was obtained, he gave his family his belongings and told them to leave the city, as he feared how his patrons might react to the ritual. This was it, everything had brought him here, he'd finaly succeed in reaching his forebear. He could never have predicted what would come out once he was done casting and a shimmering portal appeared... Blood started pouring out of it, a trickle at first, but it quickly increased in volume and force. A deluge, a cataclysm, there was no end to it. The poor Zephyr was the first to be absorbed by the scarlet liquid, he only had time to realize he'd opened a door for something horrific before he was engulfed by it.

Now having direct access to Aurora, the realm of blood slowly gushed through the portal, merging with everything that it touched and becoming more for each creature it ate, its consciouness growing and becoming more for each of its victims. Like this the city was lost in a few hours, most of its population lost or consumed by the aberration as it flooded streets and shifted its disturbing form around all obstacles. The few residents who managed to flee, left everything behind them never intending to go back. This included the mage's family he had warned to leave, who watched in horror the consequences of his actions unfold from beyond the city walls.

Fallout

However, before the creature could expand further than the city it had consummed, the spell wore off. Due to almost all of the creature's mass still being in the deep ethereal and putting an extreme burden on the magicks, all of it was suddenly shunted back to where it came from. Pulling with it everything it had touched, from roads and buildings to every creature it had reached. The portal closed as quickly as it opened. The city which had stood there proudly for centuries now reduced to a grim crater.

Within its demiplane, the entity was experiencing an extreme change brought about by the multitude of minds now intertwined within it. At first it was pure chaos, all pulling and pushing in different directions within it, however sometimes these motions and thoughts would intersect, creating a sort of harmony that slowly swept over the entire weave of minds. Like this something new was born, the all consuming tide, the living city, the Scarlet King. A being who intended on making all creation a part of its beautifull, harmonious existence.