He is after the power of the Holy Machine Soldier and plots to conquer the Suda Doaka World. In the fourth set, the one on the right is a body double whose true identity is Bug Korozo (in the Q&A section of Comic Bonbon, Bug Korozo was introduced as a body double for Sieg Korozo. SD Gundam Gaiden Memorial Book also explains that he is a body double, not the real Sieg Korozo). In the movie version, Sieg Korozo himself becomes Bug Korozo. After Zeke's brain is fused and transplanted into the remains of Runerex, and the remains of the machine soldier destroyed in the battle on the Pangaea World are absorbed, he is reborn as Rune Korozo.