The Bible describes a time when Earth will be visited by a burning heavenly body called Wormwood (also known as, Nibiru or Planet X). Before Wormwood arrives, God's angels seal the foreheads of 144,000 Hebrew descendants with the name YHVH, who will endure the coming calamities and become spiritually cleansed, even unto death.
The elite of Earth prepare and hide in caves. As the rest of humanity is oblivious to approaching doom. The closer Wormwood approaches, meteors and asteroids strike the Earth, then the sky and Earth move and the oceans "reel to and fro." Fires spread. Nuclear meltdowns will be inevitable, which will leave much of the Earth's surface inhabitable. (Note: Meteors are the first signs of advancing doom.)
Babylon is destroyed by Wormwood. Perhaps the West (Europe and America) are all destroyed, as these are the remaining powers of the "Roman Empire" ???
God's angels announce to the whole world to fear and worship only God and warns not to worship the Beast or accept his mark on the hand or forehead.
Satan causes a tsunami to try to kill the believers who survive Wormwood and who still remain on the surface of earth. As his minions and deceived are still hiding underground.
Two anointed witnesses preach truth to all the world. They have powers to stop all evil attacks. They teach the world the true name of YHVH and true faith.
Underground cities would operate using a control system to distribute food and supplies among the survivors. The system would operate under a leader who is seen as the savior/protector of humanity. This leader eventually claims to be God and forces all to bow down in worship to him. The bible calls this person the Beast. The Beast allows provisions only for those who accept his 666 mark.
For 3 1/2 years Earth survivors struggle with famine, plagues, and subjugation of the Beast's system. Many outcasts are killed for their refusal to serve the Anti-messiah or accept his mark. Eventually the two witnesses are killed and their dead bodies lay in the streets for 3 days. They resurrect and go up to the heavens. Humanity rejoices at their death.
The veil separating Heaven and Earth is revealed and the demonic entities of this world are finally seen by all humans. The Beast is revealed to be aligned with the demonic entities.
A great battle, called Armageddon, concludes where God's angels (led by God's Messiah) fight against the armies of this world. The God's armies subdue the armies of this world and the Beast and Satan are imprisoned.
The bible promises God will bring us to a New Earth. The 144,000 and the other survivors who do not accept the mark of the Beast go to this utopia Zion singing and rejoicing.
Read Revelation 20 for a more detailed description of the very end.
Choose this day whom you will serve. You cannot serve two masters. Repent means change your bad habits that prevent you from serving God. In humility as God to come into your heart and teach you His ways. Trust in God and lean not on your own understanding. For in Joel 2:32 God promises:
The Destroyer is almost here.
YHVH is my shepherd; I shall not want.
He makes me lie down in green pastures: He leads me beside the still waters.
He restores my soul: He leads me in the paths of righteousness for His name's sake.
Yea, though I walk through the valley of the shadow of death, I will fear no evil:
for Thou art with me; Thy rod and Thy staff they comfort me.
Thou prepare a table before me in the presence of mine enemies:
Thou anoint my head with oil; my cup runneth over.
Surely goodness and mercy shall follow me all the days of my life:
and I will dwell in the house of the YHVH for ever.