"Salvation for all humanity."
Amakusa Shirou himself had another name for it-the future of humanity.
The Greater Grail was the crystallization of the Einzbern family's third true magic, Soul Materialization. Granting wishes, reaching the Root, and the like were merely byproducts of its primary objective.
Achieving the complete third magic was the original purpose for which the Greater Grail had been created.
Amakusa Shirou intended to use the Greater Grail as a medium to draw an unimaginably vast amount of magical energy from the planet's ley lines, then use that energy to perform Soul Materialization on all humanity.
Soul Materialization was, in essence, what people called eternal youth and immortality. Once it was complete, the soul became a perpetual motion engine, granting humans an inexhaustible source of magical energy.
On the surface, it seemed like a perfect plan.
In reality, however, even setting aside the consequences of materializing the souls of all humanity, the process itself presented quite a few potential problems.
The model for the Soul Materialization Amakusa Shirou sought to achieve came from the "Winter Saint," Justeaze Liesrich von Einzbern, hereafter referred to as Justeaze.
Justeaze was a homunculus created by the Third Magician's disciples in their attempt to reproduce the third magic, using the Third Magician himself as their model.
She did indeed possess the ability to perform the third magic, but it required several years and an enormous amount of magical energy, and could only be used on a single person.
In other words, the third magic achieved through her had no practical value in terms of widespread application.
Amakusa Shirou's solution was simple and brutally direct.
Without accounting for the time required, he would extract the entire planet's magical energy to support the Soul Materialization of all humanity.
This was precisely where the problems began.