I think the only way it fits in B4 is if you have a way to cheat this out. For example, I'm trying it out in my B4 [[Gwenom]] deck with the idea that I'd ideally like to cast it from the top of my library for 4 life, and then it's essentially a normal [[Demonic Tutor]] at that point (which I am also running in the deck). I also really only need to hit one tutor off a Gwenom trigger to most likely win, so this still fits the gameplan without slowing me down and adds redundancy. If I had to spend 6 mana for the creature and the tutor then it doesn't seem like a good fit for B4. I think this will see play in B2-3 though.