Obviously the card is well known for being the main payoff for a blue devotion deck but he is that little bit tastier than usual in this list for a couple of reasons
If a card allows you to cast a prototype spell without paying its mana cost, like Omniscience, for example, you can choose to cast the prototyped version of the spell for free, if for some reason you want the smaller version
It hasn't been antiquated by later rules for size
The power of being able to rummage through your deck every turn is being overlooked by some, especially in this format with aftermath and eternalize cards
The "Bracket Tax": Is the Game Changer Worth the Slot
In 2010, WotC closed a loophole that allowed premium foil reprints, making the promise even stricter after some collectors felt it violated the spirit of the list