Now, that would have a beautiful synergy with aflatoxin. Not only malignant cells do no damage, and you are able to pull the trick against even 'fully immortal' decks, but also the creatures opponent manages to play have high chances to miss against you (add a dusk mantle) and deal much less damage.
Add some other
and
cards and an eclipse, and you pretty much rock.
Bone wall could also work, because malignant cells with 0 attack (and bigger creatures if thy miss) would not reduce it's counters.
Also, I guess black cat even with 1 attack would still do no damage because he reduces his attack by 1 with his own ability. It would only change anything if opponent decides to buff him.
Also I guess black cats make great synergy in
duo with diamond shields.