Breath of Fury attached to another creature you control.
You control any number of other untapped creatures with total power 4 or greater.
An opponent cannot block creatures you control.
Steps
Activate Seraphic Steed's saddle ability by tapping any number of other creatures with power 4 or more, causing it to become saddled until end of turn.
Declare Seraphic Steed and the creature with Breath of Fury attached as attackers.
Seraphic Steed triggers, creating a 3/3 Angel creature token with flying.
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 Angel token, then causing you to untap all creatures you control and to get an additional combat phase after this one.