Howlsquad Heavy by tapping it, adding ({R} magic symbol) for each Goblin you control.
Activate
Aggravated Assault by paying ({3} magic symbol) ({R} magic symbol) ({R} magic symbol) , causing you to untap all creatures you control and to get an additional combat and main phase after this one.
Repeat.
Notes
Howlsquad Heavy creates a 1/1 Goblin creature token that will have haste during each combat phase, leading to infinite creature tokens with haste and ETB.