What do we know about the historic Padmasambhava? I had heard Padmasambhava referred to as a semi-mythic figure. Some of his reputed activities would fit a mythic character. However to what extent is he also a historical figure. What do we know about the historic as opposed to mythic Padmasambhava and what if any historic sources do we have about him and his activities.
The Tibetans think of Padmasambhava as the second most important person for their lineage.

http://www.dharmafellowship.org/biographies/historicalsaints/lord-padmasambhava.htm

Here is a sample from the link above - more is available for your reading or study


  There is no doubt in the mind of every practitioner of Tibetan
  Buddhism that the second most unique and extraordinary exemplar of our
  whole lineage after Pramodavajra himself, was the powerful Lord
  Padmasambhava, the Wisdom Master who was chiefly instrumental in
  bringing the tradition to Tibet. Known as the Lotus Guru (padma-guru),
  the Saint Lama (guru Rinpoche) of Tibet, and as a "second Buddha",
  Padmasambhava1 shines with the incomparable brightness of the morning
  star in the world's firmament of stellar saints. Long before he was
  born, mystics and prophets were signaling his advent. During his life
  he drew the respect and veneration of kings and emperors and after his
  death the multitude made his memory into an imperishable icon of the
  Absolute.


The history offered is extensive so will let this quote be the introduction to a very long web page.