There's nothing like a fresh new large fall set to get the blood pumping for any Magic player. Theros is still quite unfamiliar ground for many, so continuing on from part 2 of Theros blue cards, I'll keep breaking down the set color-by-color and card-by-card, picking up from right after an expensive monster to a cheap counterspell:
Stymied Hopes - You know, for a card that's straight-up worse than Condescend in two important ways, this still isn't a bad counterspell. Soft counters usually get underrated because they're pretty bad in the late-game, but this is quite good at setting up an early-game tempo advantage.
Swan Song - Another cheap counter? And it's an Annul variant? Wow, the development team really wanted there to be answers of some kind to the Gods, didn't they? If this lost the card type restrictions and could counter artifact, creature, and planeswalker spells, it'd be much better - as-is it's serviceable, but pretty narrow in its applications and with the not-insignificant drawback of giving an opponent a pretty good air beater.
Thassa, God of the Sea - Thassa is a crazy-strong member of her marquee cycle; I know I'd play an indestructible enchantment that allowed me to give out unblockability with an activated ability if it cost 2U, and the fact that she scries and, obviously, turns into a 5/5 beater if you have high enough devotion push her over from good to great to insane. It certainly helps that her activated ability can target her, so as long as she's a creature you're nearly guaranteed to hit for at least 5 damage per turn. Weirdly, the blue god might be the most straight aggro of them all - someone in R&D is apparently a fan of Merfolk beats decks.
Thassa's Bounty - I like the kind of parallelism in this design. The mill portion of it is probably marginal most of the time, but it has a pleasing symmetry. It's also some of the best card draw in Theros Limited, and there are definitely some self-mill tricks to do with it, particularly in Standard.
Thassa's Emissary - A 3/3 for four mana with Curiosity built-in is crazy-crazy good in Limited, and only in the kind of big-beaters-for-everybody slow environment that Theros has could blue get away with it. The fact that this has bestow is pretty subtly strong, since you can stick it on one of your evasive midrange guys turn six and suddenly have an evasive fatty that fills your hand until you draw into something more finisher-y.
Triton Fortune Hunter - And right after Thassa's Emissary we have another way to draw cards as we beat face. Is the design team perhaps trying to subtly hint something to us about blue aggro? Anyway, this is good because it automatically mitigates the inherent card disadvantage of Auras, and is even more build-around than the other heroic creatures.
Triton Shorethief - I have this affection for 1/2s for one mana that can't be explain. True story: Back when I was a new player eagerly poring through the archives of all Magic cards ever printed I was baffled that Savannah Lions was considered to be better than Devoted Hero. Anyway, this is all part of the aforementioned Merfolk-aggro conspiracy in R&D, yadda yadda.
Triton Tactics - A lot of words for what amounts to giving two creatures +0/+3 and tapdowntouch. One blue mana is very cheap for giving your opponents one of the most hellish combat phases imaginable, really, especially since this is part of the cycle meant to trigger two heroic guys at once.
Vaporkin - In a set that's chock full of strong-for-their-cost small blue creatures, we can't get a straight-up 2/1 flyer for 1U, and we have to settle for a Welkin Tern? The mysteries never cease.
Voyage's End - How many times do I have to say "scrytrips are really good" before it gets old? I'm gonna say it again, which goes double since this is removal. Sure, bounce is the softest kind of removal, but still, it's hella versatile.
Wavecrash Triton - Huh, those Tritons really like stopping untaps, don't they? Anyway, as a 1/4 for 2U with a strong defensive heroic ability, this is good as a big, unmoving glacier of a blocker, especially with the redundant-but-trollish Triton Tactics, or as a harassing attacker.