I came across this article in Lions Roar, on the nature of the Tibetan practices of Vajrayana, the diamond vehicle.
Karma Chakme Rinpoche describes a path that consists of the unification or integration of the generation stage (the visualization of a deity or deities) and the completion stage (which in this case refers to recognition of the mind’s nature). This path is presented as two things that can be practiced simultaneously and do not necessarily have to be practiced separately. The song has two parts: what is to be understood and what is to be meditated on. The meaning is profound and extensive. What is to be understood is the actual view behind all deity meditation, and what is to be practiced is the main meditation of this path.
It strikes me that a path to enlightenment involving deity visualisation must be deeply concerned with those deities. It seems more appropriate to the early Bon shamans than to monks, but the article focuses on the transcendent nature of the whole. I thought it was an interesting read.