They are a race of creatures called the Inda that was engineered by the Jark Matter to serve as basic footsoldiers. Indas are mass-produced and outfitted with combat gear, turning them into Indavers.
Even though Indavers are capable of speech, their helmets muffle their voices, making it so the only things that come out are the sounds "Gyoi! Gyoi!" or "Dabe! Dabe!".
The Indavers were used by the Jark Matter to take over the 88 Constellation Systems, forming the majority of the Jark Matter military.
Later on, an elite team of Indavers was assembled into the Jark Sentai GoIndaver to counteract the Kyurangers and prevent them from going back in time. However, they proved to be easily outmatched by the Kyurangers and were ultimately destroyed.
Space Shogunate Jark Matter