he IYI sign – one of the most ancient, unarguably Bulgarian symbols. It is hard to determine when exactly it came into use. Our ancestors placed it on fort walls, cliffs, flags, amulets, on bones used for divination, on rite breads, as well as on different objects of daily life. This means that it was exceptionally important to them. The ancient Bulgarian symbol is present even on the ceramics from Mino- an Cyprus dating back from XVI century BC. The early Christians used the IYI sign before the appearance of the cross and later on – alongside it. The IYI symbol was a sign of the Dulo clan, from which descended the great Bulgarian rulers Kubrat and Asparukh, it was the seal of Ivan Shishman and a symbol of Boris or Simeon. Several scientist determine it as a symbol of Tangra (Tengri), although he was depicted with a circle with a dot in the middle. It is a common opinion that the IYI sign is more likely a Sun symbol, linked with the seven planets, which the ancient Bulgar- ians knew and observed. They worshipped the Sun, as a supreme deity, personified by Tangra. “Tangra is the spirit of the Universe. He has no image and personification, be- cause an image is something, but the spirit is everything and everything is just spirit.” In this sense, the IYI sign symbolizes the might- iness of the all. The earthly ruler as a vicar of the gods among people, is identified with the strength of unity and power. Others decipher in the symbol an abbreviation of the name of the supreme Thracian god Sabazios. It is possible that the mysterious ancient symbol IYI was transported to Asia by Thracian tribes who inhab- ited our land, as evidenced by many historical sources. Its wide use and dissemination give reason to assert with certainty, that it had a protec- tive function as a carrier of divine magical power.