When resolving an attack made against a INFANTRY or BATTLESUIT unit whilst that unit is within 3" of a friendly DRONES unit, if the wound roll is successful, you can roll one D6; on a 2+ that DRONES unit suffers 1 mortal wound and the attack sequence ends.
Building an army? Create, validate and share your list with New Recruit, army builder for Warhammer 40,000 8th Edition and many more games.