Breath of Fury, and Splinter Twin

Prerequisites

• Breath of Fury on the battlefield
• Splinter Twin on the battlefield
• Breath of Fury attached to a creature you control that can attack this turn
• Splinter Twin attached to another nonlegendary creature you control without summoning sickness
• An opponent cannot block creatures you control

Steps

1. During your combat phase, before attackers are declared, activate the creature with Splinter Twin attached by tapping it, creating a token copy of the creature with haste
2. Deal combat damage to an opponent using the creature with Breath of Fury attached
3. Breath of Fury triggers, causing you to sacrifice the creature with Breath of Fury attached, then attach Breath of Fury to a creature token you control, untap all creatures you control and to get an additional combat phase after this one
4. 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