http://www.furaffinity.net/view/1844585/

When FANG gets into a skirmish with the Warrior lord of Oen, Genbu Daishogun http://www.furaffinity.net/view/161710/ the Behemoth Prometheus ended up taking a powerful blow to protect the two smaller members of the team, Francis and Ferdinand. This act of selflessness left a huge crack on the chest of the silent giant which did not heal unlike all other previous damage to it.

While examining the damage, Sir Gilbert discovered a lock within the armor plating which becomes undone, opening the torso of the beast, revealing a young looking cat... the true form of Prometheus.

Promy is the prototype of sorts to Francis and Ferdinand, his collar and bangles made of heavy iron that he uses to interface with his armor. Unlike his younger "brothers" whose mana flows freely almost rolling of their fur, Promy's mana is focused inwards. He's been in the armor for so long that he doesnt remember to do most things like the need to eat, or talk, or go to the bathroom, but Francis and Ferdinand are filled with zeal of the prospect of helping out their older brother.