This article is about Cluster Gems. You may be looking for The Cluster.
There is no helping them, they're too broken. The beings who used to be in those shards are so shattered, they don't know who they are or what's happening around them. They just seek out other Gems, looking for the missing pieces of themselves, trying to make themselves whole.
In general, Clusters take the form of limbs joined together to other appendages. The limbs are of mismatched colors, such as dark and light blue, rust, violet, olive green, mint gray, pale green and dull yellow, indicating that they originally belonged to different Gems.
A cluster that consists of a purple and blue arm fused together.
Referred to as "Mini Cluster Gem" in the model sheets, this cluster consists of a blue hand and red foot fused together.
Referred to as "Hand Hand" in the model sheets, this cluster consists of a purple and green hand fused together.
Referred to as "Hand Cluster" and "Hand Cluster Gem" in the model sheets, this giant variant of a cluster appears to be comprised entirely of limbs conjoined together in a single hand-and-forearm-shaped body, wrapped in what looks like a dark grey cloth. At its core, the fusion is comprised of four different shattered Gem Shards that are physically fused together. It possesses four large eyes. Its irises and visible Gem Shards are green, yellow, blue and purple. According to Garnet the four Gems were the shattered fragments of shattered Crystal Gems.
A cluster that consists of a green and red foot fused together.
Referred to as "Arm Leg" in the model sheets, this cluster consists of a yellow leg and a green arm fused together.
A cluster that consists of a gray arm with a red and blue hand fused together.
Referred to as "Patient 1" in the Nightmare Hospital episode credits,  and as the "Bed Mutant" in its model sheet. This cluster has six arms and two legs. It takes a more human form, however two arms take the place of where a head would be and has two arms sticking out of its right side. Its right leg also ends with a mismatched lower leg that is much smaller than the part above. The limbs are in various colors such as orange, teal, gray, blue, and a dull purple. The location of its gem is unknown, assuming it is visible.
Referred to as "Patient 2" in the "Nightmare Hospital" episode credits, and as the "Hallway Mutant" in its model sheet. This cluster has three arms and two legs. It has two large lumps where its face would be. Its left arm acts as a leg and is very long, huge and muscular. Attached to it is two parallel hands. It has two right arms. One of its legs is very small, not allowing it to act as a real leg. It comes in many mismatched colors, including yellow, spring green and dull purple. The cluster with the same appearance made a cameo in Earthlings, which was not explained since the "Hallway Mutant" was bubbled, and most cluster gems are unique.
Referred to as "Mouth Leg Mutant" in the model sheet, a cluster that has 6 feet but uses 4 of them as arms. Two of the feet are dark purple and the rest of its body is dull red. On the bottom it has a vertical mouth that opens to reveal a single eye. It also has a dull yellow arm as a tail.
Another cluster with a gray-blue hand, wrist and a dull red foot, but it appears to be bigger.
Referred to as "Mouth Torso Mutant" on the model sheet. A dull blue cluster with two legs, a round torso body and purple arms. It has a large mouth on its torso.
A cluster with a red leg, a yellow leg, a red round body and a large pink arm.
Referred to as "Hand Body Mutant" in the model sheet. A humanoid cluster with a red head with a single blue eye, and a yellow hand like body with three folded "finger arms" at the back.
A giant white-beige hand. The bottom is not seen, but it can walk.
Referred to as "Arm Eye Mutant" in the model sheet. A big cluster with a violet round body, a pair of blue feet, a blue hand on top and a reddish eye on the center.
A big hand cluster that is half red and half violet.
A small cluster with a blue arm and orange leg.
A big green and light blue cluster with three green fingers, four light blue fingers, and a light blue foot.
Referred to as "Foot Arm Mutant" in the model sheet, a cluster with a light green head that has one eye and mouth on its face, a light blue body and left hand, a giant green foot as it's right arm, and purple lower body.
The Hand Cluster's gemstone is a mix of four different gems joined into a single gemstone. It's located on the center of its "palm".
The gemstone of the six-armed Cluster Gem - three shards fused at one point. One is teal, the other red, and the other gray.
A smaller Cluster taking the form of two forearms has two Gem Shards fused together into a V-shape, with smaller pieces stuck around the joint. One is blue, the other is purple. The shards are internal.
The gemstone of the cluster with a round violet body, three blue limbs, and an eye.
Big White Hand Cluster's gemstone.
The gem of the cluster with three lumps.
The gemstone of the Cluster with a Light Green head that has one eye and mouth on its face, a light blue body and left hand, a big green foot as it's right hand, and purple lower body.
The gemstone of the cluster with a big blue hand and pink foot.
The gemstone of the Blue Hand with seven fingers and a foot Cluster.
The gemstone of the lumpy Cluster Gem. A large purple squarish shard, with small yellow and blue shards attached.
The gemstone of the small cluster with a blue hand and red leg.
When the Earth was no longer fit to be a Gem colony, Homeworld Gems decided to create the Cluster. Because the Cluster project was a hefty task, Homeworld Gems decided to create prototypes. They took the shattered remains of Crystal Gems from the Rebellion and forced their Gem Shards to fuse together through an unknown process. It has resulted in a new gemstone that holds the consciousness of the Gems fused with it. When this artificial Gem projects its physical form, they appear to be distorted monsters as they are composed of shards of former Gems, only pieces. These prototypes were left in the Prime Kindergarten Control Room, where they stayed dormant for thousands of years.
Steven and Garnet encounter Cluster Gems in the Kindergarten, the Hand Cluster, and six smaller Cluster Gems. The appearance of the Clusters is so horrifying to Garnet that she becomes unstable to the point where she almost un-fuses. Ruby, through Garnet, states she believes the Cluster Gems were created as punishment by Homeworld for w:c:su:The Rebellion. The Cluster Gems are eventually "poofed" by Garnet and currently reside within one of her bubbles in the Burning Room.
Two Clusters are sighted across roads and taken to Dr. Maheswaran's workplace, mistaken as victims of car accidents and treated by doctors at the Hospital. Later, they break into the halls and try to attack Steven, Connie and Dr. Maheswaran, only to be poofed by Connie with Rose's Sword and then bubbled by Steven.
Peridot and Steven are assaulted by several of them when attempting to escape the Kindergarten before Steven forms a bubble and the Crystal Gems rescue them. This is the second time where the Cluster Gems are shown to have facial features (i.e., mouth, eyes); the first time being "Keeping it Together".
A Cluster Gem that looks similar to the bulky one from "Nightmare Hospital", was captured by Jasper and caged in the Beta Kindergarten, but managed to escape with a few Corrupted Gems during Jasper's battle against Smoky Quartz.