Heavy Silver is an uncommon silver-white metal that can only be found on the seafloor at depths surpassing one kilometer. It is extraordinarily hard and posses amazing ductility under high temperatures, it is also an excellent conductor of soul power. In fact, it is so good that it can amplify soul power and give it a five to ten percent boost.
Heavy Silver was not without its own flaws. It is simply too dense, bestowing upon it an extraordinary weight. For instance, a piece of Heavy Silver that is less than a third of a meter long is over 300 kilograms in weight.
Heavy Silver is rarely found in cities that are located further inland. It is instead much more common in seaside towns and acted as an important source of income for these seaside towns.
Whether it is used for industrial purposes or for manufacturing mechas, it is still an excellent metal that was hard to come by. If Heavy Silver is produced in excess, it will still be impossible to use it in large-scale mecha manufacturing. It's weight also restrict it's applications in mecha manufacturing. It is much more prevalent in large, solid state soul devices.