The Caulder Missile Launcher is an "Ultimate Weapon". It was developed by the IDS and used by Greyfield against the 12th Battalion. It was presumed to be a weapon that annihilate the city where Brenner is hiding in.
According to Isabella, both Lazuria and Rubinelle were provided hundreds of Caulder Missiles, all programmed to be launched at the opposing country at the same time. The resulting force would destroy the world ten times over.
The missile's explosion was similar to a nuclear weapon, but it is unclear if it leaves any radiation behind like a real nuke.