Breath of Fury + Temur Ascendancy + Seraphic Steed
Breath of Fury
Temur Ascendancy
Seraphic Steed
Infinite combat damageInfinite combat phasesInfinite death triggersInfinite creature ETBInfinite creature LTBInfinite mana creatures you control can produceInfinite creature sacrifice triggersInfinite untap of creatures you control
How it works
Declare the creature with Breath of Fury attached and Seraphic Steed as attackers.
Seraphic Steed triggers, creating a creature token.
Deal combat damage using the creature that has Breath of Fury attached.
Breath of Fury triggers, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to the creature token, then causing you to untap all creatures you control and to get an additional combat phase after this one.