Magar of the Magic Strings + Warrior's Oath + Day's Undoing

Magar of the Magic Strings

Warrior's Oath

Day's Undoing

How it works

1. Cast Warrior's Oath by paying its mana cost, causing you to take an extra turn after this one and to lose the game at the beginning of that turn's end step.
2. Activate Magar by paying 1, noting Warrior's Oath and putting it face down on the battlefield as a 3/3 creature.
3. Activate Magar by paying 1, noting Day's Undoing and putting it face down on the battlefield as a 3/3 creature.
4. During your next turn, deal combat damage to an opponent using the face down creatures that have Warrior's Oath and Day's Undoing noted. The creatures trigger.
5. Resolve the first trigger, casting a copy of Warrior's Oath without paying its mana cost. Resolve the copy, causing you to take an extra turn after this one and to lose the game at the beginning of that turn's end step.
6. Resolve the second trigger, casting a copy of Day's Undoing without paying its mana cost. Resolve the copy, causing you to end the turn. This will prevent the Warrior's Oath trigger from causing you to lose the game.
7. Repeat from step 3.