Title: Religion in Bulgaria
Content:   By far the dominant religion in Bulgaria is Eastern Orthodox Christianity, professed by the prevalent ethnic group, the Bulgarians, who are adherents of the Bulgarian Orthodox Church. Approximately 60% of the Bulgarians belonged to the church as of 2011. Other Orthodox churches represented in the country by minorities are the Russian Orthodox Church, Ukrainian Orthodox Church, Romanian Orthodox Church and Greek Orthodox Church. Christianity was established in the First Bulgarian Empire under Boris I in the middle of the 9th century, although it has had its roots in the Balkans since the 1st century and the mission of Apostle Paul. The rise of the Bulgarian Empire made the Bulgarian Orthodox Church autocephalous in 919, becoming the first new Patriarchate to join the initial Pentarchy. The Bulgarian Orthodox Church is the oldest among the Slavic Orthodox churches and has considerably influenced the rest of the Slavic Orthodox world by means of its rich literary and cultural activity in the Middle Ages, as well as by the invention of the Cyrillic script in Bulgaria.
Title: Bulgarians
Content:   The First Bulgarian Empire was founded in 681. After the adoption of Orthodox Christianity in 864 it became one of the cultural centres of Slavic Europe. Its leading cultural position was consolidated with the invention of the Cyrillic script in its capital Preslav at the eve of the 10th century. The development of Old Church Slavonic literacy in the country had the effect of preventing the assimilation of the South Slavs into neighbouring cultures and it also stimulated the development of a distinct ethnic identity. A symbiosis was carried out between the numerically weak Bulgars and the numerous Slavic tribes in that broad area from the Danube to the north, to the Aegean Sea to the south, and from the Adriatic 
Title: Bulgars
Content:  the Bulgar residence in Pliska and Palace of Omurtag were inspired by the Byzantine architecture is considered indisputable. Christianity had already begun to penetrate, probably via their Slavic subjects, when it was adopted in the First Bulgarian Empire by Knyaz Boris I in 865 as a state religion. There was interest in Islam as well, seen in the book Answers to the Questions of the King of the Burgar addressed to him about Islam and Unity by the Abbasid caliph Al-Ma'mun (813–833) for the Pontic/Bosporan Bulgars, while it was officially adopted in Volga Bulgaria as a state religion in 922.
Title: First Bulgarian Empire
Content:  despite all measures, Christianity continued to spread, reaching the members of the Khan's own family. Omurtag's eldest son Enravota, seen as pro-Christian, was disinherited and eventually converted to Christianity. After refusing to renounce his faith, he was executed by orders of his brother Malamir c. 833 and became the first Bulgarian saint. The attitude of the Bulgarian rulers to Christianity is seen in the Philippi Inscription of Khan Presian: "If someone seeks the truth, God watches. And if one lies, God watches. The Bulgarians did many good things to the Christians [the Byzantines] and the Christians forgot, but God watches."
Title: First Bulgarian Empire
Content:  The First Bulgarian Empire became known simply as Bulgaria since its recognition by the Byzantine Empire in 681. Some historians use the terms Danube Bulgaria, First Bulgarian State, or First Bulgarian Tsardom (Empire). Between 681 and 864 the country is also called by modern historians as the Bulgarian Khanate, or the Bulgar Khaganate, from the Turkic title of khan/khagan borne by its rulers. It is often further specified as the Danube Bulgarian Khanate, or Danube Bulgar Khanate in order to differentiate it from Volga Bulgaria, which emerged from another Bulgar group. From the country's Christianization in 864 and the assumption of the imperial title by its rulers in 917/927, the country is also referred to as the Principality of Bulgaria. In English-language sources, the country is often known as the Bulgarian Empire.
Title: First Bulgarian Empire
Content:   For almost two centuries after its creation, the Bulgarian state remained pagan. The Bulgars and the Slavs continued to practice their indigenous religions. The Bulgar religion was monotheistic, linked to the cult to Tangra, the God of the Sky. The worship of Tangra is proven by an inscription that reads "Kanasubigi Omurtag, a divine ruler ... performed sacrifice to God Tangra". The ruling Khan had an important place in the religious life: he was the high priest and performed rituals. A large sanctuary dedicated to the cult of Tangra existed near the modern village of Madara. The Bulgars practised shamanism, believed 
Title: Christianity in the 9th century
Content:  After its establishment under Kubrat, the new First Bulgarian Empire found itself between the kingdom of the East Franks and the Byzantine Empire. Christianization then took place in the 9th century under Boris I. The Bulgarians became Eastern Orthodox Christians and the Bulgarian Orthodox Church was created. In 863, a mission from the Patriarch of Constantinople converted Tsar Boris I of Bulgaria to Christianity. Boris realized that the Christianization of his subjects by the Byzantine mission would facilitate the undesired spread of Byzantine influence in Bulgaria, as the liturgy was carried out in the Greek language, and the newly established Bulgarian Church was subordinate to the Church 
Title: First Bulgarian Empire
Content:  the state and the Church under Boris I, and the creation of the Cyrillic Script in the country, were the main means to the final formation of the Bulgarian Nation in the 9th century; this included Macedonia, where the Bulgarian khan, Kuber, established a Bulgar state existing in parallel with Khan Asparukh's Bulgarian Empire. The new religion dealt a crushing blow to the privileges of the old Bulgar aristocracy; also, by that time, many Bulgars were presumably speaking Slavic. Boris I made it a national policy to use the doctrine of Christianity, that had neither Slavic or Bulgar origin, to bind them together in a single culture. As a result, by the end of the 9th century the Bulgarians had become a single Slavic nationality with ethnic awareness that was to survive in triumph and tragedy to present.
Title: First Bulgarian Empire
Content:  the Byzantines much more conciliatory. In 870, at the Fourth Council of Constantinople, the Bulgarian Church was recognized as an autocephalous Eastern Orthodox Church under the supreme direction of the Patriarch of Constantinople. The adoption of Christianity was met with opposition by large numbers of the nobility. In 866 BorisI faced a major rebellion of the boila from all parts of the country. The insurgency was crushed and 52 leading boilas were executed along with their whole kin. After BorisI abdicated in 889 his successor and eldest son Vladimir (r.889–893) attempted to restore paganism but his father took arms against him and had him deposed and blinded.
Title: First Bulgarian Empire
Content:  Around 870 the Bulgarian Church became an autonomous archbishopric. The decree of autonomy under the nominal ecclesiastical jurisdiction of Constantinople was far greater than could possibly have been achieved under the Papacy. Following the Fourth Council of Constantinople the Byzantine clergy was re-admitted to Bulgaria and allowed to preach in Greek. However, as a result of the Council of Preslav in 893 Old Bulgarian was declared the official language of the state and the Church and the Greek-speaking Byzantine priests once again had to leave the country. Thus, from that point, the church was entirely staffed by Bulgarians. BorisI's successor SimeonI was not content to leave 

Question: What is the religion of First Bulgarian Empire?
Answer: Tengrism.
Tengriism.
Tengrianism.
Tenggerism.