Breath of Fury + Seraphic Steed + Frostcliff Siege
Breath of Fury
Seraphic Steed
Frostcliff Siege
Infinite creature LTBInfinite creature ETBInfinite creature sacrifice triggersInfinite death triggersInfinite combat phasesInfinite untap of creatures you controlInfinite mana creatures you control can produceInfinite combat damage
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.