"It's easy to manipulate the powerless."
Everyone knows that blue can do a lot... but it generally can't do flat-out creature kill. Of course, as any milling deck featuring a Time Ebb can attest, sometimes you can get the desired results with a little creativity. As part of blue's "trickery" effects, it can reduce a creature's power or swap a creature's stats around - of course, if you swap the stats of a critter with 0 or less power, it's going to drop dead on the spot!
A reliable way to repeatedly cut a critter down to size is Silvergill Douser, so long as he's got a decent number of merfolk buddies around. Deepwater Hypnotist is a natural partner, lopping 3 points off a critter's power after any turn he attacks. Best of all, Merfolk Thaumaturgist is a merfolk who can perform the necessary power-swap, knocking 'em dead turn after turn.
Of course, if killing a dangerous creature is good, taking it is even better! Spawnbroker is a cheeky way to do it - temporarily shrink some towering behemoth to 1 or less power, and you can trade it for the now-useless Broker himself. At the end of the turn, your new friend returns to his former ferociousness, and the Spawnbroker remains a vanilla 1/1 once he's in play. Sounds like a good trade to me!
Of course, Spawnbroker can only make one trade. If you really want to start a collection, look no further than the always-aggravating Vedalken Shackles. Over the course of a longer game you should amass enough islands that you can grab virtually anything, but if your opponent drops something truly colossal, a temporary drop in power will render it snatchable. The Shackles don't care if the stolen creature's power hops back up - so long as it's a pipsqueak when you steal it, you'll keep it so long as those shackles remain tapped! Always trading out for the best creature on the board is great, but if you'd rather not make those kinds of annoying decisions, take the worry out of it by simply feeding the stolen creature to Miren, the Moaning Well every turn before grabbing another one. Still think blue's only able to stop creatures on the stack?
