Third Magic

Heaven's Feel, the Cup of Heaven. For further details about it, you should either play the Heaven's Feel route in the game Fate/stay night or, if you're patient, wait for the animated film version of it.
…Well, I'll touch upon it lightly at least. It is a mystery that exists in a different dimension from magecraft, one of the final goals that magi seek. Impossible feats that cannot be accomplished in the current era no matter how much time or budget you devote are called magic.
There are currently five magic in total. The third amongst them—that which the Einzberns have sought for two thousand years is the Third Magic, “Heaven's Feel.” It is true, unquestionable immortality accomplished by materializing the soul. It is definitely a miracle that would undoubtedly result in the salvation of humanity should it be implemented. Sieg is unmistakably evil for having stolen away the possibility of making it a reality.

Fate/Apocrypha material: Fate/Apocrypha Encylopedia