Mental activity in the daytime creates a latent form of habitual thought which again transforms itself at night into various delusory visions sensed by the semi-consciousness. This is called the deceptive and magic-like Bardo of Dream.
MilarepaIn horror of death, I took to the mountains - again and again I meditated on the uncertainty of the hour of death, capturing the fortress of the deathless unending nature of mind. Now all fear of death is over and done.
Milarepa