Breath of Fury attached to another creature you control that does not have summoning sickness and that has a power of one or greater.
Otepec Huntmaster does not have summoning sickness.
An opponent cannot block and kill creatures you control.
Steps
Declare the creature with Breath of Fury attached as an attacker.
Ghalta and Mavren triggers, creating a X/X Dinosaur creature token that is tapped and attacking.
Activate Otepec Huntmaster by tapping it, giving the Dinosaur haste until end of turn.
Deal combat damage to an opponent using the creature with 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 Dinosaur token, then causing you to untap all creatures you control and to get an additional combat phase after this one.