Gaster is a member of the Hyper-Zoanoid Team Five in the Japanese animated series, Guyver. Developed by the Chronos Corporation's leading scientist Dr. Hamilcar Barcas, Gaster was designed for ranged combat as a heavy artillery unit. His body generates two highly volatile liquids that react explosively when combined. Dischargers on his forearms can shoot jets of these fluids at targets and detonate them. On his expansive shoulders are eighteen organic missiles filled with these fluids. When launched, Gaster can direct the missiles telepathically.
The Guyver: Bio-Booster Armour (1990 OVA)
When the Hyper-Zoanoid Team Five attacked Sho Fukamachi's high school, Sho became the Guyver and fought them. Gaster intended to bring a quick end to the fight by blasting the Guyver to smithereens with his missiles. Thancrus intervened by destroying the missiles, stating that they would also destroy the Guyver's control medal which they were supposed to retrieve. Thancrus fought Guyver I alone until he was suddenly killed by Guyver III. Gaster lashed out at Guyver III by launching all his remaining missiles at once, but Guyver III destroyed all the projectiles with his Sonic Buster. With Guyver III's guidance, Sho attacked Gaster who tried to hold him off with his liquid explosives. Sho was able to defeat Gaster by striking his fluid sac with his vibro-blade. Gaster became doused in his own liquids wihich reacted with each other and exploded, destroying him.
Guyver: The Bioboosted Armor (2005 series)
Following the betrayal of Lost Number commando Aptom and the conflict between Zoalords Archanfel and Richard Guyot, the surviving members of Team Five were assigned to defend Chronos's Relic's Point base beneath Mt. Minakami. The team split up and Gaster remained in the control room while Derzerb and ZX-Tole went to hunt down Aptom, unaware that the Lost Number was now capable of spawning duplicates of himself. One such duplicate had disguised itself as an ordinary Chronos soldier and ambushed Gaster in the control centre. Gaster's body was completely absorbed by Aptom, who gained his abilities as a result.