Padmasambhava was probably an historical character, but has been elevated to the Bodhisattva pantheon. He has many different forms. In this image he is portaryed as a siddha, but wears a bhikṣu's robe, a pandit's hat, and the implements of a siddha. In his right hand he brandishes a vajra held in the warding off evil mudra; while in his left hand he cradles a skull cup filled with Amṛta - the ambrosia of the gods which gives immortality. In the crook of his left elbow is his katvanga or magical staff which, like the Śaivas', is a flaming trident decorated with severed heads in various stages of decay.
Padmasambhava played a crucial role in establishing Buddhism in Tibet where he is revered as a second Buddha particularly by the Nyingma school. He used his magical powers to subdue the demons of Tibet in order to allow Buddhism to take root there. In Tibet he is referred to as Guru Rimpoche (Precious Teacher), or the Vajra Guru. His mantra is also known as the Vajra Guru mantra.
Mantra
Siddhāṃ
Tibetan - Uchen
Tibetan Calligraphy by Rob Gibbs
Transliteration
oṃ āḥ hūṃ va jra gu ru pa dma si ddhi hūṃ
oṃ āḥ hūṃ vajra guru padma siddhi hūṃ
Notes
Footsteps on the Diamond Path contains a commentary on the Vajra Guru Mantra. In this comentary each syllable or word has many esoteric associations. For instance oṃ, āḥ and hūṃ represent the "supreme essence" of Body Speech and Mind (what would be called the Three Mysteries in Shingon, I think). While vajra, guru, padma, siddhi and hūṃ represent the supreme essence of the five Buddha families, which vajra, jewel, lotus, karma, and Tathagata respectively.



