Buddhist, although his ministers were not (730-740 A.D.), the
Buddhists wished their religious buildings to be kept separate from
Hindu temples but that, in spite of protests, life-sized images of
Hindu deities were erected in them.[321] The ritual too was affected,
for we hear several times of burnt offerings[322] and how Bodhibhadra,
one of the later professors of Vikramasila, was learned in the mystic
lore of both Buddhists and Brahmans. Nalanda and the other viharas
continued to be seats of learning and not merely monasteries, and for
some time there was a regular succession of teachers. Taranatha gives
us to understand that there were many students and authors but that
sorcery occupied an increasingly important position. Of most teachers
we are told that they saw some deity, such as Avalokita or Tara. The
deity was summoned by the rites already described[323] and the object
of the performer was to obtain magical powers or siddhi. The
successful sorcerer was known as siddha, and we hear of 84
mahasiddhas, still celebrated in Tibet, who extend from Rahulabhadra
Nagarjuna to the thirteenth century. Many of them bear names which
appear not to be Indian.

The topics treated of in the Tantras are divided into Kriya (ritual),
Carya (apparently corresponding to Vinaya), Yoga, and Anuttara-yoga.
Sometimes the first three are contrasted with the fourth and sometimes
the first two are described as lower, the third and fourth as higher.
But the Anuttara-yoga is always considered the highest and most
mysterious.[324] Taranatha says[325] that the Tantras began to appear
simultaneously with the Mahayana sutras but adds that the
Anuttara-yoga tantras appeared gradually.[326] He also observes that
the Acarya Ananda-garbha[327] did much to spread them in Magadha. It
is not until a late period of the Pala dynasty that he mentions the
Kalacakra which is the most extravagant form of Buddhist Tantrism.

This accords with other statements to the effect that the Kalacakra
tantra was introduced in 965 A.D. from Sambhala, a mysterious country
in Central Asia. This system is said to be Vishnuite rather than
Sivaite. It specially patronizes the cult of the mystic Buddhas such
as Kalacakra and Heruka, all of whom appear to be regarded as forms of
Adi-Buddha or the primordial Buddha essence. The Siddha named Pito is
also described as the author of this doctrine,[328] which had less
importance in India than in Tibet.

On the other hand Tarana