[A-Z April Blogging] [V] Vajrayāna Buddhism
The first wave, called Hīnayāna, corresponds to the original teachings of the Buddha (see p37 of The Celestial Empire). Game-wise, Hīnayāna Buddhism is mostly restricted to the southern provinces of the map on p28 of TCE, and in particular to the Tai-speaking peoples of the campaign (see p22 of TCE).
The second wave, called Mahāyāna, corresponds to a later stage of Buddhism that incorporates devotional practices and ideals of compassion from much later on than the original teachings of the Buddha (see p38 of TCE). Game-wise, Mahāyāna Buddhism covers the eastern half of the map on p28 of TCE, and in particular the Sinitic world, i.e., China, Korea, Japan, and Vietnam. Most of the Buddhist sects and schools described within TCE are Mahayanic.
The third wave, called Vajrayāna, or Tantric Buddhism, corresponds to yet a later stage of development of Buddhism based on esoteric writings called tantra. This latter stage emphasises esoteric teachings, including normally frowned-upon practices such as sex, or magic, or the consumption of meat or alcohol, under the strict guidance of a teacher however, see p39 of TCE. Vajrayāna Buddhism also makes use of alchemy, yoga... the aim is to attain enlightenment more quickly. In geographic terms, Tantric Buddhism is restricted to the provinces in the centre of the map on p28 of TCE: Buryatia, Outer Mongolia, Inner Mongolia, Amdo, Central Tibet, Ladakh, Sikkim, Bhutan. This does not mean, however, that Vajrayāna Buddhism didn't reach China — on the contrary: it has a rich history of presence there, even though it has always been the religion of a minority of people.
As written on p91 of TCE, Early Tantric Buddhism, known as Mìjiào (密教), was just one of the many Buddhist sects active under the Táng. Just like the Mahayanic Buddhist sects, it arrived to northern China via the Silk Road at the beginning of the Táng Dynasty. Early Tantric Buddhism received sanction from the emperors of the Táng Dynasty and was mostly popular within aristocratic circles and at the court. After the fad for Mìjiào passed, it disappeared as a stand-alone sect, but it had had time to influence the other Táng Buddhist sects, and in particular Early Chán (p90 of TCE) and Tiāntái (p92 of TCE).
A first revival of Vajrayāna took place under the Yuán, because it was the state religion of the Mongol Dynasty, see p93 of TCE. Suppressed under the xenophobic Míng, Vajrayāna resurfaces under the Qīng, again as the state religion of the Manchu Dynasty. From the Yuán onwards, however, Vajrayāna in China is felt as a foreign religion, or as the religion of ethnic minorities (e.g., the Tibetans). The only Chinese Buddhists interested in Vajrayāna are those versed in magic practices, e.g., the use of the magical Siddhaṃ alphabet.