Gastal is a post X-Day Hyper-Zoanoid that appears in the Guyver manga. Created by Luggnagg de Krumeggnic and his group of rogue Zoalords, Gastal was to serve as their catspaw in capturing Sho Fukamachi. Despite its size and intimidating appearance, its combat ability was lacking and it relied on its cloaking ability to hide itself. Gastal was capable of making itself completely invisible; even the Guyver's sensor globes had difficulty detecting its presence.

Gastal was deployed to spy on Sho and Bio-Freezer when they attempted to rescue Aptom from Cloud Gate. Aptom was freed from confinement but his body was severely damaged and required Zoanoid bio-matter to absorb in order to heal. Gastal revealed itself and fought against the heroes, only to be defeated and consumed by Aptom. However, Gastal had been implanted with an organic control unit containing the DNA of the Zoalord Cabraal Khan, and so when Aptom assimilated Gastal and the control unit, Khan was able to assume psychic control over Aptom.