I'd agree with Mondschwein and LadyMapi on not wanting to test most of this set with the notable exception of the spell lands. (And the Blue Made-For-Commander changeling, because I feel like you can do some Dumb Stuff with that.) This cycle seems like a great option for land-based strategies or in fleshing out a utility land section. Here's my power ranking of them, with an asterisk in from of each one I'm hoping to test. Anyone else interested in these?
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Bretagard Stronghold--Lifelink AND vigilance AND 2 +1/+1 counters?!
Travel Preparations, eat your heart out. Yeah, you can't play it earlier than T4 and yeah, it's not great in aggro due to the tap clause, but if Zendikar Rising has taught us anything it's that cheap spells strapped to tap lands are pretty great for aggro. I'm pretty high on this one.
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Port of Karfell--the best critter in your GY is hopefully better than a 4/4 trampler (see the Slumbermound).
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Gates of Istfell--Baby
Sphinx's Revelation for only 1 more?! A+. Great for refilling in the late game, which is when you'd want to cash this in.
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Gnottvold Slumbermound--great colors for lands, and making a 4/4 is really good on its own. One of the stronger ones.
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Immerstrum Skullcairn--discard and a bolt is really solid, especially in the late game. Only loses points for the sorcery-speed clause, but anything else would be busted.
Great Hall of Starnheim--I think this one will play better than it looks, as it provides a way to upgrade a creature of yours to Serra Angel, which is a very attractive prospect in a board stall. When you're ahead, it's still good, but ultimately it doesn't change how much removal your opponent is looking for, so it seems fairly self-balancing to me.
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Skemfar Elderhall--small removal and a couple of elves is nice, but it's pretty mediocre for small sorcery-speed removal. Probably better in a combat-heavy deck as you can leverage dealing damage in combat, but you're likely losing a creature in a trade at best, so I can't be too high on this one.
Surtland Frostpyre--the sweep and scry is nice, but it comes down really late for a 2-damage wrath. Sure, it can clear out a clogged board, but it's not going to take out the stuff you care about. Again, it's the reoccurring theme of it being really hurt by being sorcery speed.
Axgard Armory--pretty specific, fairly costly tutor. Would generally want this in an aggro deck.
Littjara Mirrorlake--only copying your own creature is fairly below-rate, and any deck that would want this likely wants
Glasspool Mimic // Glasspool Shore instead. If Glasspool Mimic didn't exist, however, I would. . . probably still rate this one at the bottom if only for power reasons. Great in EDH, though.
Sorry for the huge images!