...{Codex Shredder}.
"Wut?"
Yeah. This card does everything. 1-of mainboard, baby.
"But... Wut?"
Let me break it down for you.
"{1}"
It's a 1-drop. I might not play this if it were any higher of a cost, but this card is aggressively costed for what it does.
"{T}: Target player puts the top card of his or her library into their graveyard."
The ability doesn't cost you anything. Drop it on T1 and start milling. While you cast other cards, you can be milling them. And then you look at what {Azorius Charm} does. I'll just leave that up to your imagination.
"{5}, {T}, sacrifice Codex Shredder: Return target card from your graveyard to your hand."
Remember that Elspeth that -3'd a turn earlier? It's back. Surprise! Yes, I'm sure I don't just want to mill you for one. I'd rather have an Elspeth. By the way, I'm gonna crack my Elixir now. Alternatively, I'll just regrow my {Dissolve} and surprise counter your bomb.
Now, there are other ways to utilize this card. Remember {Thoughtscour} me, {Snapcaster Mage} my {Supreme Verdict}? This can do the same thing, albeit not as well, it's what we have in standard. This is elspecially relevant against {Chandra's Phoenix}, where milling them can come back to bite you.
I'd also like to mention that {Codex Shredder} turns Scrylands into $5 off-color Guildgates.
What do you guys think about it?
If you run shredder you need to run {Trading Post}
Not necessarily. While they're an amazing combo, you shouldn't have to do that to win the game. Especially in UW. But if you play both, more power to you.
It makes playing it note worth it. esp in uw. Get both out and thats a lock.