I don't think either the Way of the Mouse card or the Bane card can be in the Black Market deck, based on the rules. First you choose 10 kingdom cards and 0-2 landscape cards. If you now have YW, BM and Mouse, you do the setup for each in turn, and they all say to choose unused cards. If instead you ended up with just BM and Mouse, and then got YW in the BM deck, it would be the same.