The improved decks can be used two times per week. If you have all three of the improved decks, then you get the buff you posted as a bonus on each use of any of the decks.
It's great and all but i just wish it wasn't 80 pcs of that 400 diamond essence. Time to get rich and start throwing some money on diamond certs.
It's better to be silent and be thought a fool than to speak and remove all doubt. What's even better is to weaponize your words to destroy anyone who dares challenge you.