Phage the Untouchable + Hive Mind + Theoretical Duplication

Steps

1. Cast Theoretical Duplication by paying {2}{U}.
2. Hive Mind triggers, causing all opponent to copy Theoretical Duplication.
3. Resolve each Theoretical Duplication, causing all players to create a token of all creatures that enter the battlefield under an opponent's control this turn.
4. Cast Phage by paying {3}{B}{B}{B}{B}.
5. Each opponent's Theoretical Duplication triggers.
6. Resolve the first Theoretical Duplication trigger, causing the opponent to create a token copy of Phage.
7. The Phage token enters the battlefield, causing its controller to lose the game.
8. Repeat from step 6 for each remaining trigger.