The God Warrior is an ancient soldier from Nausicaä of the Valley of the Wind. It appears in the beginning of the film and later on film when Kushana order it to kill all ohmus with power. He was melted with toxics and died.
They are giant biomechanical beings (otherwise known as "Giant Warriors") considered largely responsible for the Seven Days of Fire. They have the ability to fly by "twisting space", and can fire devastating energy beams. These abilities are fueled by atomic energy, and contact with them is known to cause radiation poisoning, which suggests that the Seven Days of Fire may have been at least partially a nuclear holocaust. The characters of the manga refer to the radiation emitted by the God Warriors as "poisonous light".
The interior of at least one dead God Warrior appears to have an operator's seat, with controls and gun mount as well as interior doors .
God Warriors were important during the Seven Days of Fire, in which they likely destroyed most of the world of the past. They eventually broke down or were destroyed and by the End of the Ceramic Era they seem extinct.
By Nausicaä's time, the metal/ceramic skeletons of God Warriors are a common sight across the landscape. However, a live God Warrior is discovered by the people of Pejite in the Pejite Pit. Princess Kushana invades Pejite  in order to gain control of the God Warrior but Lastelle escapes on the Pejite Brig with the Control Stone. The brig crashes and Rastel passes the control stone to Nausicaä. The control stone is tracked down by Princess Kushana, to the Valley of the Wind but Nausicaä forces her to withdraw.
Kushana later confronts Nausicaä about the location of the control stone. By then, however, she has given them into the care of Asbel, Ratstel's brother and prince of Pejitei.
Eventually the God Warrior comes to life, but believes Nausicaä is his mother. Nausicaä feels conflicted, as she wants the God Warrior to die but pretends to love it. She eventually decides to give in to her motherly role and she names it Ohma. Together they travel to Shuwa where they destroy the Crypt.