Griselda is a feminine Zoaform that appears in later chapters of the Guyver manga. Her form appears similar to some of the Zoalords, but she is not affiliated with Cronos. She works for Zeus' Thunderbolt as the right hand of Agito Makishima, leading the Libertus in his name.
Shizu Onuma and her family have been serving the Makishima family for many years, tending to their properties and caring for Agito in his youth. When Agito first donned the Guyver, he let Shizu and her grandfather Yohei in on his secret, and although Yohei did not approve of Agito's darker ambitions, he continued to serve faithfully. Shizu had lived under her grandfather's care since her parents were killed in an accident and grew up with Agito, offering him support in any way that she could. When Agito began his struggle against Cronos along with Sho Fukamachi, she and her grandfather sheltered the Guyvers and their friends for a brief time in the Makishima family lodge located near the town of Takeshiro. It was not long, however, before Cronos discovered the lodge and the group were forced to abandon it.
After the destruction of Relic's Point, both Agito and Sho had disappeared. It was highly probable that they had both died during the event, but Shizu and the others held on to the hope that they were both still alive and would return one day. In the months following X-Day however, the group began to lose that hope and Shizu was starting to lose her mind. Their hope was restored when Guyver-III finally reappeared during a battle in Tokyo between the Lost Number Aptom and the re-optimized ZX-Tole.
Not long after the Guyvers' return, Shizu's grandfather was killed by Zoanoids whilst trying to protect Agito. With no other family, Shizu joined Agito when he returned to the United States and became his most trusted lieutenant in Zeus' Thunderbolt. Guyver-III would later attack Cronos Headquarters in Arizona, abducting one of their top scientists and the materials he would need to create his own army of Hyper-Zoanoids. After long, painstakingly delicate optimization procedures, Shizu was transformed into Griselda, a proto-Zoalord capable of directing the Libertus in battle and protecting them from the psychic control of Cronos' overlords. She has proven herself instrumental in Zeus' Thunderbolt's continued success against Cronos, particularly in Guyver-III's second attack against their Arizona HQ. Unfortunately for Fukamachi and the others in Japan, Agito no longer regards them as allies, and so neither can Shizu.
Shizu is a compassionate girl at heart, but she is utterly devoted to Agito and his ambitions. While she may hope to one day help Agito let go of his rage, she will not allow anyone to stand in the way of his plans. Nonetheless, her dedication to Agito has not rendered her as cold-hearted as him. Even during a conflict between Sho and Agito, she would not threaten Sho's friends the Segawas, who she still regards as friends even after she left them to be with Agito.
As Griselda, Shizu acts as the commander of the Libertus and holds power over them in a manner similar to the Zoalords control over Zoanoids, though perhaps not as absolute. She is a capable fighter as well, possessing strength, speed and stamina far above the human norm. Hanging from her head while in zoaform are two large sheet-like tendrils that function in a similar manner to the high-frequency swords of a Guyver, capable of lashing out at high speeds and carving enemies to pieces.
As well as controlling the Libertus, Griselda can also block the psychic waves of the Zoalords, preventing them from seizing control of the Libertus. She also possesses some kind of healing ability and is able to repair the Libertus' wounds with a touch.
As a proto-Zoalord, Shizu's lifespan may have been reduced following her optimization. It is unknown how long she has left to live.