Please forgive me for this. I'm not completely in my mind right now.
Recently, I was literally thrown into the Fate series fandom, so I am all about it nowadays, so when i returned to the fandom of SU, I could not refrain from mixing the two.
I was innocently wandering around the threads about the 'In Too Deep' event, when a post caught my eye. It said that the red hand that smacked the cockpit that Steven and Peridot were looked like Connie's. It may be a joke, but I started speculating about it and this eldritch abomination weird story came up.
*WARNING: SORT OF SPOILERS BUT NOT QUITE ABOUT THE HEAVEN'S FEEL ROUTE OF FATE/STAY NIGHT*
This starts with Dr. Priyanka Maheswaran going Mad Scientist after witnessing the power of the Gems and the Gem Mutants in "Nightmare Hospital" She allows Connie to continue seeing Steven in order to have a clueless informant of the Gem activities as well as access to unique Gem knowledge and, more importantly, to Steven.
She wants to have humans to harness gem powers, and Steven, as the only successful hybrid of both races, is crucial to her plans. She starts running tests on him and the Gems without their knowledge, with the excuse of medical checks or scientifical curiosity. This allows her to mine loads of knowledge about Gemkind and the mixed nature of Steven.
Upon learning of the Cluster's existence and the plan to reach it, Dr. Priyanka starts devising a plan to use its inmense power for her own benefits. She starts to experiment on her daughter so as to turn her into a suitable vessel for the Cluster.
Taking advantage of the absence of the Gems (as of Back to the Barn), she sneaks in the Crystal Temple and steals the Gem Mutants' gemstones, as well as some Corrupted Gems. Knowing that incorporating such an alien, unstable and inorganic matter into a human directly would be lethal or uneffective, and that Steven's case was exceptional; she uses her combined knowledge about Steven, Lion and Corruption to create her own way of doing so: the Shard Worms.
She implants them in Connie's body and succeeds in integrating the Gem Mutant particles with her organism; turning her into a "Lesser Cluster" of sorts and changing her skin, hair and eye colour. The Worms grow inside her until they form a whole entangled net of Gem/organic tissue that violates her function as a human being. The worms are latent unless she tries to use her gem powers; in that case they will activate and start devouring the extra energy, causing her lots of pain and making her new power undetectable.
Sometime later, the Gems find the Cluster and destroy its embrionary physical form. However, when they are about to recover the huge gemstone cluster that composes its core, they are attacked by a mysterious creature and chased away, losing the cluster in the process.
The creature (an overgrown Shard Worm under Priyanka's control) absorbs the gemstone composite and returns to her lab. Splitting it into several little worms, the doctor implants them within Connie and succeds in turning her into the vessel of the "Greater Cluster". Apparently, this has no effect into Connie's physonomy, psyche or body function, except for some sudden manifestation of Gem powers that force Priyanka to reveal that she has been experimenting on Connie "in order to let her fight at Gem level"
However, following the implantation of the Cluster in Connie's body; a strange apparition starts roaming through Beach City. Called "The Cluster Amorphous" it is a shapeless being that lacks a recognizable face, limbs or even a gemstone. Composed only of hard light, it devours and corrupts everything in its path, focusing specially in Gems.
People (Gem and human alike) start disappearing as the sightings and confrontations with the creature increase. At the same time, Connie starts to have visions of the Amorphous feeding during the night, and slowly develops a connection with it, feeling its hunger as her own. She becomes so attuned with it that she starts wandering at night and becomes able to devour Jasper. She also can use it to expand her senses.
At that moment, Priyanka (who had been using the creature for her own purposes) is confronted about the true nature of it, and she reveaks the truth: It is a being composed of the pain and suffering of the shattered Gems of the cluster, the hatred and malevolence of its creators and her own ill will, all of it is sealed away by Connie's good nature. However, as it is so massive and powerful, it starts manifesting as a separate entity.
Hurt and full of despair because of her mother's deception and manipulation, Connie rejects her violently, causing her powers to go rampage. Priyanka tries to control her through the Shard worms in her body, but she purges her body of them and kills her, embracing her internal malice. Realizing that she is the Amorphous, she fully merges with it and becomes Cluster Connie, an evil and warped version of her previous self with unmeasurable amounts of Corrupt Gem Magic Energy at her disposition. Her essence becomes so nocive that anything tmshe aproaches either corrodes or becomes contaminated by it
Filled with resentment and desire of revenge against both Gemkind and Humankind, she kidnaps Steven in hopes of using him as an axis to create a magic singularity that completely drains both Earth's and Homeworld's lifeforce (organic and Gem alike), effectively wiping both species and destroying everything.
She devours the CGs when they come to rescue Steven and then spits them out in a "Corrupt" indefinite state, turning them into her own powerful and evil soldiers, twisting their minds and providing them with an almost unlimited supply of energy. She retreats behind them in a fortress of her own making where she can accomplish her plans
Steven, from his captivity, tries to reach the real "good" Connie that
still exists within Cluster Connie; while a bunch of good gems and human warriors team up to battle the "Cluster Gems" and fight their way towards CC's stronghold, in order to use the definitive weapon against her and defeat her once for all.