Infinite creature ETBInfinite creature LTBInfinite combat damageInfinite combat phasesInfinite death triggersInfinite mana creatures you control can produceInfinite creature sacrifice triggersInfinite untap of creatures you control
How it works
Declare Grub and the creature with Breath of Fury attached as attackers. Grub triggers, putting a -1/-1 counter on the creature with haste, and then creating a tapped and attacking copy of that creature.
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 token with haste, then causing you to untap all creatures you control and to get an additional combat phase after this one.
Move to your next combat phase, and declare Grub and the token that has Breath of Fury attached as attackers.
Grub triggers, putting a -1/-1 counter on the creature with Breath of Fury attached, and then creating a tapped and attacking copy of that creature.