I really like stampede, despite the fact that it's parasitic, but it needs different reminder text. Perhaps "Creatures you control with stampede can't be blocked unless all creatures with stampede are blocked." Or "Each attacking creature with stampede can't be blocked unless they all are," which is a bit more casual but still understandable. There needs to be a "you control" or a specification that indicates attacking creatures, otherwise there's rules confusion as to whether a non-attacking player with a Stampede creature makes all my stampede guys unblockable.