Ladder of Heaven

Ladder of Heaven (天の梯子 Ten no Hashigo) is a weapon stipulated as the strongest and evilest.

Description
Although many details about the Ladder of Heaven remain a mystery, it has been revealed that the reconstruction during the ten years after the war mankind speaks proudly about is nothing more than a mere weapon specialized for massacre. The Ladder of Heaven, given the name of the strongest and evilest weapon, is what connects heaven and earth. Born from the Great Gastrea War, it is a powerful weapon that saw the defeat of humanity.

In short, it is a super-magnetic linear projector, or a very powerful railgun, that can fire a metallic projectile up to 800mm in diameter at close to light-speed. The weapon was originally designed to fight Gastrea, but the area surrounding it has since been overtaken by the Gastrea and the module has since been abandoned. The original plan, as explained by Sogen Saitake, was to mount the weapon on the moon and snipe Gastrea from there, with the bonus being that they would have a power advantage over the other countries if they ever re-conquered Earth. It was part of the plan to "push Japan into becoming a great world power " after the Gastrea were eliminated.

However, the weapon does have many flaws that were presented during its usage in the first story arc. The first one being that it broke when Rentaro used his Varanium arm as a projectile instead of the designated projectile, whose size was different. The second flaw was presented right after Rentaro loaded the projectile, which was that the railgun could not be operated remotely, either due to the lack of maintenance or a flawed design, forcing the weapon to be used manually from its control station. The third flaw is that the super-magnets needed for the railgun to operate interfere with electrical signals, subsequently cutting off communications via telephone and any other form of communication that depends on the transference of electrical signals.

In the end, the Ladder of Heaven was used to defeat the Model Scorpion Stage V Gastrea, as a Varanium projectile shot at near light-speed prevented even Stage V's from regenerating.