Gustav is a prototype Hyper-Zoanoid developed at Cronos Headquarters in the Guyver manga. Covered in hyper-dense chitinous armour, this Hyper-Zoanoid specimen was intended to surpass the capabilities of previous mega-muscle Zoanoids such as Zencrebe and Derzerb. However, Gustav had yet to be given a specialized weapon before it was destroyed in an attack by Zeus' Thunderbolt and its new Libertus soldiers.