With the crown item debate on items and the items of the week button, etc, as thoughts in the background of my mind, I have begun thinking of items I would design.
My first thought would to be a 'Cape of Forethought'. It would be as a normal crown item of its class (a few % accuracy, %dam, %defense), but instead of a specific card granted, it would have a slot where you could insert a treasure card from your 'stash' Of course, once used, it would be gone. This only slightly alters the dynamics of the game (you could always discard to get to the same card), but it would allow you make sure your items were carrying the spells 'just right' for your next boss battle.
I would add a staff like Headmaster Ambroses and call it 'Ambrose's staff of the spiral' which would give a super card that would be unlike anything else, it would be called 'Ultra spiral' and it would be a balance thing and give out maybe 500 attack. Yeah.
i would have a pet called "evil malistair" and it would give you +900 life +800 mana and give you the card "malistair" that does 700 attack and half amount will heal you. like the rotting fodder card. does 160 you get healed 80 but instead attack 700 heal you 350. level 50+ only.