Russia's invasion of Ukraine has killed tens of thousands and triggered the biggest confrontation with the West since the 1962 Cuban Missile Crisis when the Cold War superpowers came closest to nuclear war.
Medvedev, who once cast himself as a liberal moderniser as president from 2008 to 2012, said Moscow was fighting "crazy Nazi drug addicts" in Ukraine backed by Westerners who he said had "saliva running down their chins from degeneracy".
Ukraine and the West have repeatedly dismissed President Vladimir Putin's assertions that Ukraine is run by fascists who have persecuted Russian speakers. Instead, they cast the war as a brutal land grab by Moscow.
In a message marking Russia's Day of National Unity, Medvedev said the task of the fatherland was to "stop the supreme ruler of Hell, whatever name he uses - Satan, Lucifer or Iblis".
Medvedev, now deputy chairman of Russia's Security Council, said Russia had different weapons, including the ability to "send all our enemies to fiery Gehenna", using a Hebrew term often translated as Hell.
Since the war began, Medvedev's rhetoric has become increasingly fierce though his published views sometimes chime with thinking at the top levels of the Kremlin elite.
Satan's weapons, Medvedev said, were "intricate lies. And our weapon is the truth. That is why our cause is right. That is why victory will be ours! Happy Holidays!"Â
