A Zodiac Gastrea is a Stage V Gastrea that has near-unmatched power.[1] Rentaro Satomi and Enju Aihara defeated the Zodiac Model Scorpion in Episode 4 using the Ladder of Heaven.
In total, there are three Zodiac models that have been destroyed; the Model Scorpion by Rentaro Satomi, the Model Virgo by the current IP Rank 2 Initiator, and the Model Taurus by the current IP Rank 1 Initiator[2]. The Model Taurus was once thought to be invincible, wreaking havoc in many parts across the Asian continent with the Stage IV Gastrea Aldebaran as its "right-hand man"[2].
Stage V's are extremely dangerous as they are not affected by the magnetic fields given off by the Varanium Monoliths, allowing them to destroy said Monoliths and pave a way for smaller Gastrea to wreak havoc upon the citizens enclosed inside the Monolith barrier. However, there are not many Stage V's due to the fact that the maximum Stage in which a Gastrea can grow to is Stage IV. Stage V's are also special as they can be summoned using certain objects, such as the Model Scorpion with the Legacy of the Big Dipper, the tricycle that the civil officers were after in the first story arc[3].