This article deals with the way the noun 'tengri which means 'heaven' and may refer to the Heaven's God, is used in Old-Turkic inscriptions from Mongolia (Orchon Inscriptions) and Southern Siberia (Yenissei Inscriptions). The inscriptions were written between the 8th and 10th centuries in the Turkic speaking nomad environment and most of them include explicit references to the ruling dynasty. In Orchon Inscriptions, 'tengri' refers mainly to the God and the God's support granted to the Ashina dynasty, pointing out the dangerous consequences of abandoning the dynasty or rebelling against it. According to the Orchon Inscriptions, 'tengri' is all-mighty and represents the most important member of the Old-Turkic pantheon. It has a dual nature - the supporting one and the punishing one. It may support its people during hardships and punish them when they disobey their ruler or the ruling dynasty. The Yenissei Inscriptions do not refer to the God's support in such an extent.