Breath of Fury attached to a creature you control that can attack this turn.
Myrel does not have summoning sickness.
An opponent cannot block creatures you control.
You control at least one additional Soldier.
You control a Mountain.
Steps
Declare the creature with Breath of Fury attached and Myrel as attackers.
Myrel triggers, causing you to create a number of 1/1 Soldier artifact creature tokens equal to the number of Soldiers you control.
Deal combat damage to an opponent using the creature with Breath of Fury attached and Myrel.
Breath of Fury triggers, causing you to sacrifice the creature with Breath of Fury attached, then attach Breath of Fury to a Soldier token, untap all creatures you control and get an additional combat phase after this one.