It is giant weapon that takes on Strelizia’s Agath Apus form. It is significantly much larger and taller than a FRANXX. It has no face like a FRANXX, a larger helm, four legs, and wing-like structures in its back. It has a long laser weapon on his forehead.
In the manga, it is thoroughly described as a colossal Klaxosaur weapon. It initially takes on the appearance of a massive colossal Klaxosaur baby-like creature. Once merged with Strelizia (anime) or a 9 Model (manga), it takes on a FRANXX appearance identical to its anime counterpart.
APE’s sole objective for seizing the Gran Crevasse was to not only gather enough cores of Klaxosaurs to build Hringhorni but to take control of Star Entity, as the Klaxosaur Princess, 001, intended to use it in order to annihilate the human population.
Dr. FRANXX describes it as the ultimate weapon and was formed as an aggregation of Klaxosaurs after eons of fusion and evolution of the Klaxo Sapiens. The Vice Chairman describes the Star Entity is a mass of life that could disrupt the universe’s peace.
Upon gaining control of the weapon, APE made applications to it and, unbeknownst to everyone involved, Papa implanted a virus in Star Entity in case 001 happened to try and reclaim Star Entity. He designed the virus as a doomsday bomb, which could only be triggered by Strelizia or any FRANXX attempting to connect with the core of Star Entity and it would be powerful enough to destroy the entire planet.
However, once the bomb was activated but failed to detonate right then, it was discovered that Hiro, as a human, was a foreign factor to Star Entity, which required a Klaxo Sapiens to operate it, which delayed the bomb from detonating by 72 minutes.
At the final minute of the countdown, Hiro and Zero Two, due to 001’s sacrifice to help them two stop the destruction of the planet, awakened Strelizia and took control of Star Entity. it then evolved into the Strelizia Agath Apus and effortlessly destroyed the VIRM fleet before the latter fled. Strelizia Agath Apus then ascended into space for a galactic battle with VIRM.