Yasak was gradually introduced in North Asia in the 17th century as a consequence of Russia's conquest of Siberia. The Tsar's relationship with natives was based on the quid pro quo principles. The annual delivery of yasak by the native representatives was normally accompanied by a state-sponsored feast and distribution of royal gifts to the natives. This compensation included tobacco, flints, knives, axes, and other useful tools. Some native populations, especially in the Far East, favoured multi-colored crystal beads. The local voyevoda could also provide the yasak-payers ("ясачные люди") with supplies of provisions such as fish oil.