Breath of Fury attached to another creature you control ).
Easy Prerequisites
Opponents have at least two creature cards in their graveyards.
Notable Prerequisites
Opponents with creature cards in their graveyards cannot block creatures you control.
Steps
Deal combat damage using
Shark Shredder and the creature with
Breath of Fury attached.
Shark Shredder and
Breath of Fury trigger.
Resolve the
Shark Shredder trigger, putting a creature card from the defending player's graveyard onto the battlefield under your control tapped and attacking.
Resolve the
Breath of Fury trigger, causing you to sacrifice the creature it is attached to, then attach
Breath of Fury to the creature put onto the battlefield in step 2, then causing you to untap all creatures you control and to get an additional combat phase after this one.
Repeat each combat phase.
Notes
If there happens to be two or more creatures with haste in opponents' graveyards, you can omit
The Fire Crystal so long as both
Shark Shredder and the creature with
Breath of Fury attached do not have summoning sickness.