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Where your unit has the Supreme Commander ability:
All of your detachments that have their HQ unit within 30 cm of the Supreme Commander unit gain the Stubborn ability.
If the unit contributes its Assault value to a close combat, or contributes its Firepower value to a firefight, then you may re-roll the die for Assault resolution. If you re-roll the die then you must abide by the second roll.
Tyranid Dominatrix — additional Supreme Commander effect
The Tyranid Dominatrix unit is a special case. Not only is it a War Engine that has the Supreme Commander ability, but for this unit only the ability has this additional effect: