Against All Odds
Each time a model in an ADEPTUS CUSTODES unit from your army, excluding VEHICLES, makes an attack, if there are no other friendly units within 6 inches of that unit, add 1 to the Hit roll and add 1 to the Wound roll. Both halves at once, on every attack, ranged and melee. That is one of the largest unconditional-looking buffs in the edition, and the condition is the whole game: your units have to be spread out. Six inches is further than it sounds once you are holding objectives, screening a deep strike and moving a Character with a unit, and the rule checks the attacking unit's surroundings at the moment it attacks, so a unit that drifted into support range loses both bonuses. Note that VEHICLES are excluded entirely, so this is an infantry, mounted and character detachment. This is not a Lone Operative detachment, whatever the name suggests; Lone Operative comes from one of its enhancements, Praesidius.