Lute, 6 years old.
Most of the time since the magic liquid metal arrived was consumed in experimenting and inspecting results, by a 5-year-old kid.
Magic liquid metal was a special metal; if you imagined armor while touching it and pour in Maryoku, the metal would take on that imagined shape—it had that property.
The advantage was that it was easy to carry if you bring only a small amount.
For that reason, it seemed to be a tool of choice for assassins.