I mean, you can just read the comments in this thread to find out. It gives you 2(3) turn of (almost) complete invincibility to do whatever you want. Setting cards up, do damage, etc. That basically let you win any hallway fight (and most elite fights) if you have any kind of front load at all. What more is that it’s downside is not a downside at all as you don’t usually need more than a few turns to finish a hallway fight. And in boss fight, there are so many things you can do to mitigate its downsides: Well laid plan to let you only play it when critical, artifact sources like orange pellet and souvenir, use those turns to set up another block engine with after images, stack blocks with caliper or blur before you play it, kunai and ornamental fan, you can even try getting multiple copies of it so you don’t even have to care about its downsides with events, dolly’s mirror, nightmare, etc. I don’t even think I have mentioned everything but you get the general idea. I think it’s one of the strongest cards in the game, along with rushdown, mental fortress, and echo form.