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These were Crystal Gems, shattered into pieces, they were buried together...
(Steven: Why aren't you moving?!)
They were forced together,
they were forced to fuse! This is wrong! I-I-I'm sorry! aghAGH-
(Steven: No, no! Garnet! You're coming undone! Garnet! Garnet! Garnet! Please! What's the matter? This isn't like you!)
~ Garnet horrified at the Cluster Gem experiments and nearly unfusing as a result.
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.
~ Peridot on the Cluster Gems.

The Cluster Gems, also known as Gem Mutants and Artificial Fusions, are an antagonistic faction of monstrous fusion experiments in Cartoon Network's Steven Universe. They were created by combining fragments of shattered gems, and serve as prototypes for a colossal geo-weapon called The Cluster.


The Cluster Gems essentially have broken minds and are unable to tell who they are or what's going on around them. When they detect Gems, they attack them in a desperate attempt to find the other pieces of themselves and become whole again. Smaller Cluster Gems are more passive and harmless, but bigger ones are more violent and are capable of harming others.


Pre Series

After Pink Diamond's supposed shattering and the end of the Gem War, Earth was abandoned by Homeworld as they saw it as no longer fit for colonization. Instead, Yellow Diamond chose to try and create a geo-weapon capable of destroying worlds, which would be dubbed The Cluster, a multitude of billions of shattered gem shards buried deep within the Earth's crust.

Prototypes were designed in preparation by forcing gem shards to fuse together through unknown methods. Once formed from the new gemstones they would form as distorted monsters with a broken consciousness. A Peridot was assigned to Earth in order to monitor the main Cluster's progress.

Marble Madness

The Cluster Gems make a semi-hidden cameo in this episode while Peridot monitored them from the control room ceiling.

Keeping It Together

The Cluster Gems first debuted in this episode. Underneath the prime kindergarten, Steven and Garnet try to discover what Peridot was after. While in the wrecked control room, one of the pillars begins to shake and a small cluster gem lunges at Steven, but Garnet poofs it. After seeing the two gem shards stuck together, Garnet throws it away from her in disgust but sees other Cluster Gems fall from the columns above. Then the pillar that they investigated breaks and from it emerges a giant hand monster.

Garnet is horrified at the creature and becomes unstable to the point of nearly unfusing. After Steven pleads with her however, Garnet regains her composure and poofs the giant cluster gem. There and then, Ruby and Sapphire's personalities each talk within Garnet, Sapphire clearly upset while Ruby is outraged at such experiments taking place.

Ruby: So this is what Homeworld thinks of fusion.
Sapphire: We couldn't have known they would do this...
Ruby: This is where they've been! All the ones we couldn't find, they've been here the whole time!
Sapphire: Rose couldn't have known!
Sapphire: IT'S NOT OUR FAULT!!!
~ It is quite possible that Sapphire worried that their first fusion as Garnet is what caused these experiments to start.

After this, Garnet commands Pearl, Amethyst and Steven that all the Cluster Gems must poofed and bubbled back to the temple.

Nightmare Hospital

Two Clusters were found across roads and taken to the Beach City hospital, believing that they were victims of car accidents. They were treated by Dr. Maheswaran and other hospital staff but later broke into the halls and tried to attack Steven, Connie and Dr. Maheswaren. It was here where Connie had to reveal to her mother her sword training, as well as tell her more about her relationship with Steven and the Gems. The Clusters were poofed and bubbled.

When It Rains

While Steven and Peridot went to the Kindergarten to investigate the Cluster, the two were attacked by several Clusters. They were saved in time by Garnet, Amethyst and Pearl.

Gem Drill

While drilling down into the Earth's crust, Steven and Peridot are attacked by other prototypes. They are blasted back into the magma and likely poofed, where Steven expresses his desire to try and help them.


A Cluster Gem was caught by Jasper alongside various other corrupted Gems, although it managed to escape after Jasper's fight with Smoky Quartz.

Homeworld Bound

In this episode of Steven Universe Future, it is shown that Yellow Diamond is repairing Cluster Gems by putting their fragments back together. It is likely that the bubbled Cluster gems would be sent to her so they could be returned back to normal.



  • The Cluster Gems are widely considered by many fans to be the darkest characters in Steven Universe.
  • They are very similar to The Amalgamates from Toby Fox's Undertale.


          StevenUniverseTitle.png Villains

Great Diamond Authority
White Diamond | Yellow Diamond | Blue Diamond | Pink Diamond

Homeworld Gems
Peridot | Lapis Lazuli | Jasper | Yellow Diamond's Pearl | Blue Diamond's Pearl | Pink Pearl | Eyeball Ruby | Navy Ruby | Holly Blue Agate | Aquamarine | Topaz | Emerald | Hessonite | Squaridot | Pyrope | Demantoid | Spinel

Fusion Gems
Sugilite | Malachite | Cluster Gems | Cluster | Unknown Quartz Fusion | Bluebird Azurite

Gem Monsters
Centipeetle Mother | Albite | Gem Cave Creature | Big Bird | Ice Monster | Invisible Gem Monster | Lighthouse Gem Monster | Slinker | Great North Gem Monsters | Grossular Diopside | Monster Steven

Robonoids | Bismuth | Holo-Connie | Marty | Frybo