O King of all the nations, the only joy of every human heart; O Keystone of the mighty arch of man, come and save the creature you fashioned from dust.
Christ is the head of us all. He is mighty God and Prince of Peace. He is the Lion of Judah. His fore-bearer, David was King of Israel, but the Messiah comes as King of the Gentiles (Nations). He bridges both the chosen ones and the nations into a single, coherent arch.
An arch held together by the perfect keystone – the One who makes all things complete; and the One who makes all fallen creatures new – by the blood of His cross.
A different way of salvation, a way that only the Everlasting God could have imagined, coming into his creation to save it from within.