Had he realized it earlier – then he wouldn’t have been tricked by the sweet lie of miracles that flew the banner called dreams.
Kiritsugu had once released a demon powerful enough to destroy the world because of his aspirations. It was too late when he finally realized his mistake. Countless people had died because of it, including Shirō’s own father and mother.
And that harbinger of Hell was still lurking beneath Mount Enzō even now.
After that battle, Kiritsugu had repeatedly visited that place with dynamite, and spent years to map out the situation of a few leylines. He had meticulously created a ‘bump’ at a location leading towards Mount Enzō. That might be the last time for him to use magecraft in his life.
The prana produced from the junction of numerous leylines will collect upon that ‘bump’ with time. When its limit is reached, a localized earthquake will be triggered deep within Mount Enzō. It would take a minimum of 30 years and a maximum of about 40 years for the ‘bump’ to break. If all his calculations were correct, then the cavern within Mount Enzō would collapse and seal away the “Greater Grail” forever.
Though he would not be able to live to see that day, Kiritsugu had done the best he could to prevent the fifth Heaven’s Feel 60 years later.