Igor (Church Slavonic: Игорь; Old Norse: Ingvarr; c. 877 – 945) was Prince of Kiev from 912 to 945. Traditionally, he is considered to be the son of Rurik, who established himself at Novgorod and died in 879 while Igor was an infant. According to the Primary Chronicle, Rurik was succeeded by Oleg, who ruled as regent and was described by the chronicler as being "of his kin".
Sviatoslav I or Svyatoslav I Igorevich (Old East Slavic: Свѧтославъ Игорєвичь, romanized: Svętoslavŭ Igorevičǐ; Old Norse: Sveinald; c. 943 – 972) was Prince of Kiev from 945 until his death in 972. He is known for his persistent campaigns in the east and south, which precipitated the collapse of two great powers in Eastern Europe, Khazaria and the First Bulgarian Empire. He conquered numerous East Slavic tribes, defeated the Alans and attacked the Volga Bulgars, and at times was allied with the Pechenegs and Magyars (Hungarians).
Following the death of his father Igor in 945, Sviatoslav's mother Olga reigned as regent in Kiev until 962. His decade-long reign over the Kievan Rus' was marked by rapid expansion into the Volga River valley, the Pontic steppe, and the Balkans, leading him to carve out for himself the largest state in Europe. In 969, he moved his seat to Pereyaslavets on the Danube. In 970, he appointed his sons Yaropolk and Oleg as subordinate princes of Kiev and Drelinia, while he appointed Vladimir, his son by his housekeeper and servant Malusha, as the prince of Novgorod.
Rurik (also spelled Rorik, Riurik or Ryurik; Church Slavonic: Рюрикъ, romanized: Rjurikŭ; Old Norse: Hrøríkʀ; died 879) was a Varangian chieftain of the Rus' who, according to tradition, was invited to reign in Novgorod in the year 862. The Primary Chronicle states that Rurik was succeeded by his kinsman Oleg who was regent for his infant son Igor.
Traditionally, Rurik has been considered the founder of the Rurik dynasty, which was the ruling dynasty of Kievan Rus' and its principalities, and ultimately the Tsardom of Russia, until the death of Feodor I in 1598. As a result, he is considered to be the traditional founder of the Russian monarchy.
Oleg (Old East Slavic: Ѡлегъ, romanized: Ōlegǔ, Ольгъ, Olǐgǔ; Old Norse: Helgi; died 912), also known as Oleg the Wise, was a Varangian prince of the Rus' who became prince of Kiev, and laid the foundations of the Kievan Rus' state.
According to the Primary Chronicle, he succeeded his "kinsman" Rurik as ruler of Novgorod, and subdued many of the East Slavic tribes to his rule, extending his control from Novgorod to the south along the Dnieper river. Oleg also launched a successful attack on Constantinople. He died in 912 and was succeeded by Rurik's son, Igor.
Olga (Church Slavonic: Ольга; Old Norse: Helga; c. 890–925 – 11 July 969) was a regent of Kievan Rus' for her son Sviatoslav from 945 until 957. Following her baptism, Olga took the name Elenа. She is known for her subjugation of the Drevlians, a tribe that had killed her husband Igor. Even though it was her grandson Vladimir who adopted Christianity and made it the state religion, she was the first ruler to be baptized.
Olga is venerated as a saint in the Eastern Orthodox Church with the epithet "Equal to the Apostles". Her feast day is 11 July.