Shugo is a mixture of Buddha, bodhisattvas and deities worshipped by various religions, or a category that considers them as one religion.
Syncretism occurs mainly when a religious belief that has established itself in a specific region and a new religion come into contact and similarities are found within their beliefs. Syncretism takes place in two styles: one completely absorbing the other or the two religious beliefs combined, giving itself a joint name. There are cases where a sect goes through changes after being introduced to a new place and then considered being heretical or the opposite case as in India, the origin of Buddhism, where it dies down. Whether the sect is considered legitimate or heretic is relative, while both parties asserting its legitimacy and 'heretics' is a label for the opposition. Normally, the sect with stronger constituents and a larger number of followers is more apt to be considered legitimate. (As with Catholic and Protestants, where they merely split when they competed with each other) Global religions, such as Christianity and Buddhism have experienced syncretism; as a result they were easily accepted, and succeeded in increasing their number of followers.
Example of syncretism
Christmas on December 25 is traditionally known as a Christian event for being Jesus Christ's birthday, however, there is no mention of this written in the Bible. It seems that Christmas originated when Christianity spread into Europe and the celebration was combined with the festival of the Winter Solstice that took place in various locations within Europe.
In regard to the myth of alchemy, Throth, the Egyptian God of Wisdom, Hermes, the Greek God, and Mercury, the Roman God, were combined as the God Hermes Trismegistos (Three times great Hermes).
In Egyptian Myths, there is the case of Throth and Hedj-wer, both the God of Wisdom, where one God absorbed the other. Throth, which was originally in the form of an African Threskiornis, and Hedj-wer, in the form of a baboon, were both Gods of Wisdom and ended up in the form of Throth with an addition of the shape of a baboon.. Ra-Atum is an example of the composite names of Ra and Atum, both of which were the Gods of Creation.
In East Asia, Taoism, Confucianism and Buddhism from India mixed with each other and are called the 'Three Great Religions of China'.