In response to the emergence of kaiju, a series of cyan power emeralds were invented that allowed its wielders to instantly create a suit of robotic armor, enhancing their strength and durability. Due to the physics-breaking nature of the gigantium used in the emerald’s construction, they are capable of increasing mass from a base engineered schematic. The size-scaling effects of gigantium are inconsistent with ranged projectiles, and so there is a greater reliance on melee armaments, such as swords and shields, for the wearers/pilots of the mecha.
Running support for the mecha pilots are teams of men and women who monitor diagnostic information, maintain supply, and cover military coordination. They also monitor kaiju activity and call in for the dispatching of mecha warriors to contain monstrous threats.
Gigantium isn’t simply used by mecha: it originally was found in the bones of kaiju. Nearly every kaiju, from the first that emerged to wreck Tokyo (because it is always Tokyo) to the most recent, have had two commonalities. The first is that they are humanoid crocodilian monsters, lacking the ability of speech but having a deadly cunning and maneuverability. The second and more worrisome is that while they start off being only two meters tall, they constantly grow larger and stronger – no upper size limit is known, but their growth rate is usually a steady incremental increase until killed.
As sometimes kaiju are spotted at different times in their growth and can even recover after being seemingly defeated only to return bigger than before, mecha likewise come in different sizes. Typically a mecha pilot will reactivate their cyan power emerald to create a larger mecha around the one they’re already wearing/piloting. In this fashion one mecha can be inside another mecha, created nested matryoshka mecha of no known upper size limit.
(I do not own the images in the above collage, and all copyrights belong to their respective owners.)
Go to another world …