There used to be a metamagic available to magicians and mystics called Filtering, which required Cleansing. For a Complex Action you made a Magic + Counterspelling test with a threshold equal to the Background Count - Initiation Grade (minimum 1). Each net hit negated one point of the background count for you, and lasted for a number of turns equal to your Magic. Guess it was too powerful to bring back into SR5.
Mind this was also a time when background count didn't penalize your [Magic] skills and such, but actually reduced your Magic attribute. If that dual natured critter had a Magic of 5 or less in that background count of 5, it'd no longer be a dual natured critter while it was in that background count.