Breath of Fury + Pestered Wellguard + Concordant Crossroads
Breath of Fury
Pestered Wellguard
Concordant Crossroads
Infinite creature sacrifice triggersInfinite creature ETBInfinite creature LTBInfinite combat damageInfinite combat phasesInfinite death triggersInfinite mana creatures you control can produceInfinite untap of creatures you control
How it works
Declare Pestered Wellguard and the creature with Breath of Fury attached as attackers. Pestered Wellguard triggers, creating a 1/1 Faerie 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 Faerie token, then causing you to untap all creatures you control and to get an additional combat phase after this one.