At the start of your Command phase, in a turn in which you have not called a Waaagh!, if you have one or more **WARBOSS** models on the battlefield (or embarked within a **TRANSPORT** that is on the battlefield), you can call a Waaagh! for a second time this battle. When doing so, that second Waaagh! only counts as having been called for **WARBOSS**, **NOBZ** and **MEGANOBZ** units from your army.
