As a 3/5 flyer with two very good abilities and very good power and toughness (just enough power to fly below Elspeth, Sun’s Champion’s radar and just enough toughness to block Stormbreath Dragon without dying), Prognostic Sphinx has ruled the block constructed season and will probably be a player in Standard in the future as well.
What I wanted to talk about is the difference between scrying for 1 and scrying for 3.
And yes, although the difference is technically 2, the difference is much deeper than that.
There aren’t many cards that scry so much. Actually only two others in the Theros block (Riddle of Lightning and Interpret the Signs, which both need the scry very badly) and no card lets you scry deeper than that in the block (actually Foresee is the only card in Magic that lets you scry for more than 3, although one could argue that Cryptic Annelid does as well). There are no other cards that let you do it continuously, especially ones which also let you do damage at the same time.
Usually, when you scry for 1, you have to put pretty much thought into it. Unless you’re pushing all lands, or all nonlands, you have to make a quick decision about whether you are going to need that card now, or in the near future and whether you can find another copy, if you need it later. Its a big decision. On the other hand, if you are scrying for three and doing it pretty reliably turn after turn, you can take another approach. You can start to think about the cards you would like to draw. You’ll get there and usually in just a few draw steps. Also, if you are attacking all the time, you have your choice of three cards each turn.
However, there are plenty of other interactions.
I mentioned the interaction with Dakra Mystic in my card spotlight just a couple of days ago. If your opponent plays Courser of Kruphix, just scry the card you least want on top of your library and use the Mystic to get rid of any unwanted cards for your opponent. How often do you see people side out the Coursers? Well, I did just yesterday against my deck that had this (admittedly unintended) combo in it.
Of course, if you yourself use the Courser, you can get most out of it by sculpting the top of you library to fit your needs. You leave a land as the first, second, or first and third, or whatever the situation warrants.
How about Ashiok, Nightmare Weaver? If your opponent is playing it, you can scry all the cards he’d like to the bottom of your library. Of course, this isn’t foolproof and in many cases wily opponents will then simply decline to use the Ashiok and thus leave you with subpar draws.
And this is only the block, although since the top your deck has such a big meaning in the block, you’ll probably find that the Sphinx is much stronger here than it would be in other contexts.
But there’s one more thing most players probably won’t think about:
The Sphinx can go through your deck at such a speed that the order you put cards on the bottom of your library might actually become relevant, especially if you control two Sphinxes. After all, since you see four cards each turn with the Sphinx (and you’ve seen at least 10 before being able to play it), it only takes you ten or so turns to go through the whole deck (assuming you bottom most of your cards, as you probably will). So, if you have been paying attention, you’ll know exactly when certain cards will come up.
Of course, you won’t be able to remember, but on the other hand, you can make notes. Just make sure those notes are unreadable by your opponent.