Emrakul, the Promised End + Erratic Portal + Unwinding Clock + Vedalken Orrery

Emrakul, the Promised End

Erratic Portal

Unwinding Clock

Vedalken Orrery

How it works

1. Cast Emrakul by paying 13 reduced by its first ability.
2. Emrakul's second ability triggers, causing you to gain control of an opponent's next turn and giving them an additional turn after that one.
3. Move to that opponent's next turn.
4. Unwinding Clock triggers, untapping all artifacts you control.
5. Activate artifacts by tapping them to add enough mana to cast Emrakul, plus an additional 1.
6. Activate Erratic Portal by paying 1 and tapping it, returning Emrakul from the battlefield to your hand.
7. Repeat until the opponent you are controlling each extra turn has lost the game.
8. Repeat for each remaining opponent.