Despite the November 1 release of Commander 2013 and the announcement of Vintage Masters on Magic Online, Theros is the number-one topic in Magic right now. The new expansion is still relatively untested and full of surprises, so continuing from the first part of the blue cards in Theros, I'll move on with my color-by-color, card-by-card breakdown of the set, picking up with collector number 51.
Horizon Scholar - This has the potential to be very solid in Limited as a sort of penultimate creature; a 4/4 flyer just won't cut it as a finisher in the slow and explosive battlecruiser-Magic environment of Theros, but this is more than enough to stave off attackers and get maybe a hit in while scrying to hit your actual gamewinner. Weirdly, the biggest blue beaters in Theros aren't flyers.
Lost in a Labyrinth - I'm in favor of scry-trips, generally, and the fun thing about this one is in addition to being a defensive combat trick you can use it on one of your own guys to trigger heroic if you're really desperate.
Master of Waves - For something with a semi-tacked-on protection from red, and that seems to encourage mono-blue play, paradoxically, the most fun you can have with a Master of Waves is in a blue-red deck. In Standard right now we have Young Pyromancer and Molten Birth, which, as turn 2 and 3 plays before a Master of Waves, make a pretty crazy-big army. The trick is getting the Master out at the optimal time, with enough blue on the battlefield to get a significant number of tokens out of him; in any case Nivmagus Elemental is an integral part of this combo. If you want to stay in mono-blue, Water Servant is an unsurprisingly good friend to Master of Waves.
Meletis Charlatan - Sure, this is good for copying your own spells and as such is primo Johnny-bait, and sure it makes for interesting politics in any multiplayer format, but there are also some hilarious karmic applications that can make your opponents' own spells turn on them. Imagine copying a big fat Sphinx's Revelation that by consequence causes your opponent to draw out their library and then lose. Comedy gold!
Mnemonic Wall - Appropriately, this was a slight source of false memories for me; I could have sworn it was printed in Mirrodin block rather than Rise of the Eldrazi, though I was probably just severely misremembering Psychic Membrane. Anyway, this is appropriate as it was in Rise, with that set's defender subtheme and the big-creature theme they both share, and can be just as much of a bulky annoyance as it once was.
Nimbus Naiad - I'm not even going to address the strawman "Bestow is too expensive!" complaints at this point. I think Confucius once said "he who looks down on pump and flying, soon gets looked down on while he's dying."
Omenspeaker - Hey, a bite-size Horizon Scholar! Sure, Omenspeaker is great as a roadblock, but I like 1/3s for two because they can be attackers that nobody is really sure how to deal with in the early game. I mean, nobody in their right mind is gonna want to trade their N/1 with her, but at a certain point you wonder if it's worth it to let all those 1-damage hits through. The face of the Oracle of Theros is more subtle than she appears. One final note - I like that the foreign-language names of so many Theros cards say "hell with it" and outright acknowledge their inspirations. She's called "Sibyl" in French, Italian, and Portuguese because dammit we all know she's the Sibyl of Cumae, why can't we acknowledge that?
Ordeal of Thassa - Design-wise, card draw as the sacrifice trigger of the blue Ordeal is rather uninspired. In actual gameplay, it's way more pump than the best evasive color normally has access to, and it draws two cards. Stick it on anything unblockable, swing repeatedly, and laugh.
Prescient Chimera - A 3/4 flyer for five wouldn't be a disappointing body in most Limiteds, but Theros isn't most Limiteds. Fortunately, repeatedly scrying more than makes up for it. Scry 1 over and over again adds up, trust me.
Prognostic Sphinx - And scry 3 over and over again probably adds up even quicker. It's a pity this is only 3 power in the air, because it's definitely not easy to deal with, with 5 toughness and that hexproof-gaining ability. Talking of that particular ability, I'm pretty sure it's something I'd never expect to see in a Magic set ever - a riff on Deep Spawn.
Sea God's Revenge - Holy hell, I think this is being ignored as a one-sided partial board sweep at common. In a format dominated by creatures that grow, whether at a cost of massive investments of time and cards as with heroic creatures or at massive mana costs as with the monstrosity creatures, soft removal can be very nearly as frustrating as the hard kind. This can very often clear enough blockers out for a relatively early alpha strike and as if that weren't enough... scry 1.
Sealock Monster - Sometimes a 5/5 defender for five mana comes in handy in this environment, and when you turn this eight-leggedy beastie into an actual 8/8, he lets your islandwalkers through. Deceptively solid.
Shipbreaker Kraken - To repeat my earlier observation - the big blue stuff here is ground-based. A 6/6 for six sans drawbacks is, shall we say, anomalous in the color, and the game-ending monstrous ability here is one of my favorites.