Masters of Camouflage
ASTRA MILITARUM WALKER and REGIMENT models from your army have the Benefit of Cover. While such a model has the Benefit of Cover for any other reason (e.g. because it is wholly within a RUIN), improve the Save characteristic of that model by 1 (to a maximum of 3+).
Ignores Cover
Weapons with [IGNORES COVER] in their profile are known as Ignores Cover weapons. Each time an attack is made with such a weapon, the target cannot have the Benefit of Cover against that attack.
To get the improved save characteristic a unit has to have two sources of Benefit of Cover, itself and something else. Ignores Cover weapons prevent a unit from having Benefit of Cover against attacks made with this rule. Since the unit has zero Benefit of cover against those attacks it does not get the improved save characteristic.