Shroud Of Despair: To Wound rolls from the abyssal Staff's shooting attacks are made against the target leadership rather than Toughness. The abyssal staff's shooting attack has no effect on vehicles. (pg. 29, Codex: Necrons)
The question is whether this works against fearless or if Imperial Guards gets to use their HQ leadership within twelve inches or if orks in mobs use their modified Ld.
And, since it is To Wound, do you use the highest leadership or the leadership that is in majority like normal To Wound?