Look on my works, ye mighty, and despair! Scrying Pool is nigh! Now, I'll be the first to admit that in decks rife with Treasures, Victory cards and Curses, Scrying Pool is rather shitty, being a more expensive, slightly better Spy. However, trashing away these aforementioned cards can allow you to draw your entire deck every turn with a single card. With Steward, you can not only get rid of all those nasty non-Action cards, but also increase the likelihood that your Potion will meet with the two coins necessary to get your first Scrying Pool. Once there, continue to trim your fat. Hopefully, you will have bought some coin-yielding cantrips, or at least some villages and coin-yielding terminals. The odds are pretty good that any given kingdom will have at least one of those. Now, it is very important to only buy Actions - absolutely nothing else. The only thing you want your Scrying Pool to trip on is your solitary Potion, which you can even trash once you feel you've gotten enough Scrying Pools. You don't want just one, as tempting as that may be: you'll need them for the end game. Once you've built up a nice action engine dripping with buying power, start to green. With any luck, this will only take a turn or two: if you've emptied enough piles buying Actions, you can just go for Duchies or Estates, while your opponent scrambles to reconstruct their engine after you discarded half of it with your Pools.
Obviously, this strategy will not work by itself. You can't get rid of all your Coppers too soon, or you'll just be left with a Steward, a Potion, and a whole bunch of useless Pools. If you have the unfortunate luck to see Scrying Pool and Steward on a board with no good cantrips or villages or terminal coin-givers, it may be better to just give it a miss and go for BM. However, this strategy shines like a supernova in two instances, and even makes one card a wee bit better, all of which happily come from the same expansion (who would have thought! intentional synergy!).
University: When University is on the board with these two cards, feel free to trash all the way down to Steward and a Potion. After that, alternate between Scrying Pool and University. The University will fill your deck with delicious coin-yielding Actions, while your Scrying Pools let you draw them - usually on the same turn you gain them. University a Festival, play a Scrying Pool, play the Festival! I could go on about Universities, but I'll save that for another article.
Vineyard: This will require a slightly different strategy. You will definitely need as many Scrying Pools as you can get, as well as any and all sources of +Buy. You will also need more than one Potion (four should do). When you feel your deck is bloated enough with Actions, and you have your four Potions and +Buys, take four Vineyards. Next turn, if your Scrying Pools don't trip too hard on the Vineyards (you'll probably want at least eight Scrying Pools), you can do the same, ending it if it's a 2-player game, and making it ridiculously hard for your opponents to catch up in a 3- or 4-player game.
Possession: While generally a weaker card, this type of deck ensures that you can play your Possession every turn, severely annoying your opponent.
This combo will trip on anything that would gum up your Scrying Pool works. If Ambassador or any Curser is in the kingdom, forget about everything said above. You may still want some Scrying Pools to clear through the muck, but you would be better served getting your own Ambassador/Curser to try to muck their deck faster. However, if Lighthouses are available, this combo can ensure that a Lighthouse is played every turn, letting you ignore deck-bloating attacks.
Works well with:
-Any Action, particularly non-terminals, and givers of coin and Buys
-University
-Vineyard
-Possession
-Lighthouse
Conflicts with:
-Any Treasures
-Actions that give Treasures: Bureaucrat, Trading Post, Explorer, etc
-Non-Action Victory cards: Gardens, Duke, etc
-Ambassador
-Curse-giving cards: Witch, Familiar, etc
-Crossroads
-Tournament
