What is agony (sakarat al-mawt), and what does the deceased see at the moment of death? And how does the soul ascend to its Creator, where does it settle, and does it visit the people of this world?

The most important thing to focus on is preparing for death with complete monotheism (Tawhid (definition)). The Hadith (definition) explains that when a believer is on their deathbed, angels with white faces descend upon them, bringing shrouds and embalming perfumes from Paradise. The Angel of Death then comes to take their pure soul, which ascends to the heavens, and its doors are opened for it. Then, it is returned to their body in the grave, where two angels come to question them about their Lord, their religion, and their Prophet. They remain steadfast, and a door to Paradise is opened for them.

As for the disbeliever, angels with black faces descend upon them, bringing coarse garments. The Angel of Death then comes to take their wicked soul, which ascends but the doors of heaven are not opened for it, and it is cast into Sijjin. Then, it is returned to their body in the grave, where two angels come to question them. They hesitate, and their evil deeds trouble them, and a door to Hell is opened for them.

Furthermore, angels descend upon the dying person, who sees them and they speak in their presence. The souls of martyrs are in the bellies of green birds in Paradise, and the souls of Pharaoh's people are exposed to the Fire morning and evening. As for the visitations of the souls of the dead to the living, there is no legitimate religious proof for this.