Xun You served as the military advisor, his Spiritual Talent would cause his army to be overlooked, and during the battle of Xuzhou, it was precisely this trick that allowed Cao Cao to escape unscathed.
If this were on the sea, as long as the weather wasn't particularly clear, Xun You could fully unleash his Spiritual Talent, ensuring Gan Ning's large ship could propel to a distance sufficient enough to launch an attack. Do you know what being overlooked means? It's seeing something but acting like you haven't seen it...
More accurately, Xun You's Spiritual Talent is about turning himself and everyone under his command into harmless passersby that no one pays attention to. Of course, if a passerby starts hitting people, they'll definitely reveal themselves.
