Injectors are ancient Gem machines that were used to embed nascent Gems in Earth's crust, where they would gestate before emerging. They are currently scattered all around the Kindergartens in a state of disrepair.
The Injectors resemble bacteriophages, which are viruses that can infect and reproduce within bacterium, sometimes destroying the bacterium itself. The bottom of the machines have one large drill, surrounded by smaller ones. Thin, jointed appendages are located near the drills, presumably for walking. The upper structures sport large, red, gem-like ornaments on the top.
The body of the rig itself seems to showcase a clear panel containing within it what appears to be either an organic heart, much like the Crystal Heart located in the center of the Crystal Temple, or an artificial womb. These seemingly organic hearts/wombs are attached to the head and feet of the machine via red and blue tubes that resemble arteries and veins, respectively.
As revealed in "Keeping It Together", injectors drill into the earth, injecting a Gem deep underground. The implanted Gem then drains the life force/energy from its surroundings in order to reach full adulthood. It then forms a gemstone, and emerges from the ground.
- In "On the Run", Amethyst refers to these as "old Gem junk".
- Injectors can hang off walls at 90 degree angles.
- However, when Pearl threw her spear at an Injector's leg, it fell right off the cliff face.
- It is stated by Garnet that if the Kindergarten is reactivated, the Injectors will power back on and continue the project.
- Their official name was confirmed in the episode "Keeping it Together".
- However, injectors were previously mentioned during Peridot's diagnostic log in "Marble Madness".
- Peridot makes a note that the injectors on Earth are outdated.
- This implies that Homeworld has grown Gems on other planets and that they are still invading them.
- As seen in "Too Far", the interior of the drill head contains a console.
- The injectors have a very similar design and function to the virus: bacteriophage, which inject their material into the host, which is repurposed to create more viruses.
- Additionally, their insides resemble organic hearts.
- According to Amethyst in "Guide to the Crystal Gems", the Injectors put "colorful goo stuff" in the ground and after time a Gem is formed.