Vadjrasattva (tib. Dorje Sempa) is considered to be
      both a bodhisattva and one of the six Dhyani (Buddhas in meditation) Buddhas.  The
      tradition that views Vadjrasattva as a bodhisattva regards him as the manifestation of the
      purity that is ultimate reality.  Vadjrasattva is also considered the primordial
      Buddha of all mandalas (geometric visualization aides as well as the homes of deities).
        He wears the robes of a bodhisattva, holding the vadjra (dorje) in his right hand
      and the ghanta bell in his left.  
      As a Dhyani Buddha, Vadjrasattva retains the same
      physical characteristics he displays as a bodhisattva, and is still recognized by his
      white color and the one vadjra he holds at his chest with his right hand.  He is
      represented both alone and in yabyum with Sakti who holds up a skull cup with her left
      hand and a katari knife in her right.  Vadjrasattva and Sakti embrace in dhyanasana
      position, both sitting cross-legged in meditative pose.