At this point the separation of the mind and body occurs.
Since the mind is now divided from the body, it is without a physical support. The gross material body is gone, and there is only a subtle body composed of light.
This subtle body lacks the essential substances received from the father and mother, and consequently the dead person has no further perception of the light of sun and moon.
Nevertheless, there is a kind of luminescent glimmering, a mental energy, emitted from the light body. This creates the impression that one can see one’s way.
In addition, all the beings who are wandering in the bardo of becoming are able to see and hear each other.
Another aspect of this bardo is that whenever the bardo consciousness wishes to be somewhere, it is instantaneously present in that very place. The only places it is barred from are the womb of its future mother and Vajrasana, the sacred place where all the buddhas attain enlightenment.
The bardo body is a “mental body,” which is why it is present in a place as soon as that place is thought of.
The mind of a dead person also possesses a certain clairvoyance, albeit tinged with defilement. It knows what other people are thinking. A recently dead person can perceive how others are using the possessions he had accumulated in the course of his life, what they are thinking about, and how they are performing the meritorious practices for his sake.
The living do not see the dead, but the dead can perceive the living.
Bardo beings congregate together and suffer from the sensations of hunger and thirst, heat and cold. They experience intense suffering as they wander in the intermediate state. Those who actually wander in the bardo are those who have failed to practice much virtue in their lives, but at the same time, have not accumulated too much evil.
Beings who have committed great evil will not experience the bardo of becoming at all. As soon as they close their eyes in death, they instantly arrive in the lower realms.
On the other hand, those who have accumulated great merit arrive at once in a buddhafield.
In general, though, people like ourselves, who are neither great sinners nor great saints, will have to experience the bardo of becoming, and this is nothing but suffering.
On the other hand, the deceased may be protected from the horrors of the bardo and attain liberation. This will happen if a person has accomplished many meritorious actions, has made offerings to the Three Jewels, has given charity to the poor, and so forth; and if others have constructed the mandala of the peaceful and wrathful deities and performed the ritual in which a piece of paper with the name of the deceased person written on it has been burned, and if empowerment has been conferred (leading the consciousness of the dead person to higher destinies).
It is rather like when a crowd of people rush together to catch and save someone from falling over a precipice. This is why it is said that we should perform many virtuous actions for the sake of the dead.
During the first twenty-one days after death, the deceased have the same sort of perceptions they had during life. They have the impression of possessing the same body and mind as before, and they perceive the same surroundings they experienced during their life.
Later on, they begin to have perceptions related to the place where they will take rebirth in the next life.
This is why it is said that the period of forty-nine days—particularly the first three weeks—is extremely important. During that time, if a lot of merit is accumulated by others for the sake of the dead, it is said that even if the people in question should be on their way to the lower realms, the compassion of the Three Jewels can lead them to a higher destiny.
After that period, however, their karma will propel them into the lower realms and, though the compassion of the Three Jewels remains unchanged, that compassion is powerless to lead them to a higher destiny until their negative karma has been exhausted.
This, then, is why it is important to accumulate a great deal of merit for the sake of the dead.
Dharma people, who are used to the practice, recognize, when they are in the bardo of becoming, that they have died. They realize where they are, and they remember their teacher and their yidam deity. By praying one-pointedly to them, they are able to gain rebirth in pure lands like Sukhavati, Abhirati, or the Glorious Copper-Colored Mountain.
It is also possible for an accomplished lama to summon the bardo consciousness of the deceased into their written names and then reveal the true path to them. By giving teachings and empowerment, he can show them the way to the buddhafields, or at least bring the bardo consciousness to the attainment of a human birth.
Everything depends on the karma, aspiration, and devotion of the deceased.
Of all the bardos, the most crucial one is the bardo of the present life. For it is now, in the bardo of the present life, that we must act and practice well, so that we will not have to wander in the other bardos.
Source: Dudjom Rinpoche. Counsels from My Heart (Kindle Locations 805-842). Shambhala Publications. Kindle Edition.