Doors of Durin, Breath of Fury, and Mortuary

Prerequisites

• Doors of Durin on the battlefield
• Breath of Fury on the battlefield
• Mortuary on the battlefield
• You have a creature card that has haste on top of your library
• Breath of Fury attached to a nontoken creature you control that has haste
• An opponent cannot block creatures you control

Steps

1. Declare the creature with Breath of Fury attached as an attacker
2. Doors of Durin triggers, causing you to scry 2, ensuring to leave the creature card with haste on top of your library, then revealing the creature card and putting it onto the battlefield tapped and attacking
3. Deal combat damage using the creature that has Breath of Fury attached
4. Breath of Fury triggers, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to the creature Doors of Durin returned, then causing you to untap all creatures you control and to get an additional combat phase after this one
5. When the creature dies, Mortuary triggers, putting the creature on top of your library from your graveyard
6. Repeat each combat phase

Results

• Infinite combat damage
• Infinite combat phases
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite mana creatures you control can produce
• Infinite sacrifice triggers
• Infinite untap of creatures you control