Alexei Navalny was asked four years ago what he'd tell Russians if he were killed for challenging President Vladimir Putin. Russia's prison agency announced Friday that Navalny had died in the Arctic penal colony where he was serving a 19-year sentence on charges of extremism. Kremlin political critics, turncoat spies and investigative journalists have been killed or assaulted in a variety of way s. The Russian opposition has lost its brightest star with Navalny's sudden death in a prison colony.