Cast Magister Sphinx by paying ({4} magic symbol) ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) .
When Magister Sphinx enters the battlefield, it triggers, causing an opponent with at least twenty life to lose life until their life total is equal to ten.
At the beginning of your end step, Archfiend of Despair triggers, causing each opponent to lose life equal to the life they lost this turn.
The opponent targeted by Magister Sphinx in step 1 loses the game due to having zero or less life.