Who will be saved from the last great disaster that will fall upon the whole world?
Through the Apostle John, God discerned those who would be harmed by disasters and those who would be saved.
God prophesied that He would pour seven disasters of His wrath in the near future (Rev 16:1-20).
It is prophesied that the way of salvation would be opened from the ends of the world in the east after WWII [the massacre of the Israelites].

The "seal of God" is the "Passover" that has the promise that every disaster will pass over us when we keep it.

God dwells in us only through the Passover. This is why God commanded us to keep the Passover as the lasting ordinance for generations in the Old Testament, and Jesus, too, emphasized that it is the new covenant that we must keep to the last day in the New Testament.