Query: When did Ruik past away?
Context: Rurik led the Rus' until his death in about 879, bequeathing his kingdom to his kinsman, Prince Oleg, as regent for his young son, Igor. In 880-82, Oleg led a military force south along the Dnieper river, capturing Smolensk and Lyubech before reaching Kiev, where he deposed and killed Askold and Dir, proclaimed himself prince, and declared Kiev the "mother of Rus' cities."