A problem we ran into. Do the house cards stack or is what you play permanent. For instance, Baratheon play salladhor saan which makes all boats not your own 0 when supported. The opponent is greyjoys and play aeron. When they choose a new card they choose victarion. Would they still get the +2 to all there ships or would sans effect still make them 0?
This is answered in the FAQ:
Q: If House Greyjoy plays his “Victarion Greyjoy” House card against House Baratheon’s “Sallador Saan” House card, are the participating Greyjoy Ships still reduced to 0 combat strength?