Spoilers so far

So I'm going to review the cards as they're spoiled. I want to talk about them from a design perspective and their uses for EDH.

Colorless:
We'll start with the big one, Ugin, the Spirit Dragon.
Ugin is a really good card. Ugin's +2 can kill your opponent on its own. Ugin is maybe the best planeswalker at defending himself on board since he comes stapled to All Is Dust. The obvious comparison is to Karn since they are both big mana colorless planeswalkers. His + can stop on board threats unlike Karn who has to act as a disrupting scepter to build toward his ult, though Karn builds faster, he is also easier to attack. Ugin's negative ability can splash your own board, whereas Karn's is always pinpoint. Karn's ult is often game winning, but that's not the point of Karn. I can see many situations where Ugin's ult is going to be a real threat that you have to stop. Ugin is going to require a non-permanent threat to stop him on his way to winning the game for you. In non-edh environments Ugin can even ult into himself and chain things together. In EDH his ult can bring some unbelievable board states to life.

Ugin was clearly designed to be the marque card of the set. He is an incredibly internally consistent card that wins the game for his controller in multiple ways. I'm expecting him to show up in Standard, Modern, EDH. He might be strong enough to show up in legacy since he murders literally everything players play in that format. In EDH you'll play him in any big mana oriented deck. Teferi, Temporal Archmage would be a great fit for Ugin, as would other artifact mana based decks. The other route is to play him in some green acceleration based deck like Azusa. He can be slotted as either a board wipe or essentially as an enchantment that does three damage a turn. The other way to think of him is as a delayed Sphinx's Revelation.

No matter what you play him in or for, lots and lots of people will be playing Ugin. The mechanics of his card set him firmly as the opponent to Nicol Bolas, particularly the ultimate. The art is reflective of this, as is the mana cost. They are setting up Ugin to be the one to oppose Bolas in the alternate future.

White:
Honor's Reward -
Bolster as a mechanic is really good at catching you back up from behind. It makes your little dudes into big dudes. Having that effect stapled to a three mana instant might have been good enough. Having that instant gain you four life is going to be very solid as you can take a hit or two while pushing with your weenie creatures and leaving your smallest creature behind, threatening to make it much larger. That they are counters means you get to permanently enlarge your smallest guy, probably making another guy your bolster target from then on. This card is pretty well designed, but just doesn't have enough impact for EDH.

Soul Summons-
Manifest as a mechanic is going to be very strange for people to get used to. This is essentially a 2 mana 2/2. I suppose having a Manifest Bear was going to be inevitable though I think it could have (or maybe even should have) been a colorless spell. Its possible Ugin is the only colorless non-artifact spell in the set because if you were doing other ones Soul Summons seems like the perfect candidate. Once you decide that his should be a colored spell basically any color would do. I would have liked this in blue since it represents an inherent form of trickery. Hilariously enough, just a 2/2 for 2 in green isn't good enough nowadays. White is fine, but I am surprised this is a colored spell. Obviously in EDH this is a way to put morph creatures into play on the cheap and its decent in conjunction with Sensei's Divining Top.  That's probably not good enough but that's where this is. Manifest as a mechanic is going to rely heavily on library manipulation to be good.

Valorous Stance-
This is obviously a crazy good card. Reid Duke spoke about it at length. I'll simply say that designing this much flexibility and strength must have cost White a lot of its budget for instants in this set. In terms of EDH I always judge white instants by Sunforger. This is a pretty damn good Sunforger target because of its flexibility, effectively being two targets in one. Outside of Sunforger this is still a good card but other effects are bigger and you'd be more comfortable draw them over having the timing based half of Valorous Stance.

Dragonscale General-
This guy is pretty damn good. The idea is that you leave your weakest creature on defense and make use of everything else, pumping up your smallest dude. You can also do the attacking pre-combat and surprise your opponent with a huge blocker if he doesn't want to block. This card plays really well with convoke. I can see this getting played in EDH decks that are either really aggressive or like the set of convoke cards, like Rhys. I love the alternate art, but the regular art is...iffy. 


Blue:
Jeskai Sage-
 This is a pretty good card. Prowess remains unchanged from KTR, and on the Sage the idea is that they don't want to block it since its on death trigger replaces itself. But if they don't block it, the Prowess can add up. Its a unique combination and it might work out in conjunction with Seeker of the Way. For the purposes of EDH, there aren't as many Blue value deck running around. Most Blue decks are either in the camp of huge mana threats or tricksy instant speed shenanigans. Jeskai Sage feels like it belongs in a Black deck. That's not to say it won't see play. Decks that want what it does want it very badly, its just not going to have a wide appeal.

Sage Eye Avengers-
This card is dangerous. It has the potential to lock your opponent out of the game in 1v1. That it costs 6 mana and doesn't protect itself are why its not being regarded with fear. I understand the idea behind it but printing something this frustrating to play against is something they won't do often. That said, the interplay between Prowess and the trigger is very cool. In EDH I can see this coming into play off a Sneak Attack or with some other haste granting effect and foiling someones best laid plans. Alt art is superior here as well.

 Jeskai Infiltrator-
This card is very odd. It might just be because of Manifest but this set has a much higher number of bazaar cards than usual. I like the idea of it hiding itself among other creatures, and only becoming hidden after it has "infiltrated" the enemy. The card has a solid logical consistency, that will unfortunately not do enough in EDH to be worthwhile.

Temporal Trespass-
I was curious how far they would go in on a delve creature. Indeed, after the shake up that delve has caused in eternal formats I was curious if we would even see the mechanic. I'm happy that they didn't shy away in the second set since delve is one of the better mechanics they've done in years. It has very obvious rewards and a pushes you to do things differently than you would if you didn't have delve cards in your deck. It's also obvious to your opponent what you're doing if you play things like thoughtscour or mental note.This card has one of the best lines of text in magic. Between this, Treasure Cruise, and Dig Through Time we basically have delve versions of the blue power, like Time Spiral all over again. This card though, unlike the others, is probably not good enough. In EDH the cheapness doesn't count for as much since in terms of time you can generally play Temporal Manipulation faster. It also eats itself, and extra-turns that are non-infinite are pretty miserable for everyone involved. Outside of EDH this is UUU, which makes it super hard to cast. It also takes 8 cards, the most of the delve spells, and doesn't replace itself in the graveyard for future delve action. I'm happy they made this card since it wouldn't have felt genuine to make delve recall and not delve timewalk. I'm happy the card that saw print is just on the edge of playable.

Black:
Crux of Fate-
This is it. The whole point of going into the past. This is also a new black board wipe. I'm curious how often the choice will be relevant. They wouldn't have made the condition if the condition didn't have a chance of mattering. For EDH it certainly has a better than average chance to be a real choice. That said, there are already plenty of wraths in Black. If you want to pay more than four mana for a wrath then there are better options. The exceptions being Skittles, Karrthus, or some other Dragon general where its a board wipe for your opponents and not you.

Gurmag Angler-
This guy is not some revolutionary reinvention of the wheel, but he is amazingly solid. A one mana vanilla 5/5 is probably as far as they are going to push delve on the creature side. He's actually a pretty solid card for EDH as well. Anything with Greater Good is probably in the market for this dude, as is Jarad. Hilariously, this guy is the opposite of what you want in Varolz since his cost starts high and gets low. He will also probably show up in eternal formats so there is that.

Hooded Assassin-
Ok, this card isn't going to be showing up in EDH for lots of reasons. It always has a shot in assassin tribal.

Soulflayer-
I've seen more buzz around this guy than Gurmag Angler, and they are like Treasure Cruise versus Dig Through Time. Sure this guy is certainly splashier and can do more overall more, but Angler is cheaper on actual mana spent, and naturally a point of power and toughness ahead. In EDH Soulflayer has a much better time of picking up abilities, but if you are playing a deck that can take advantage of those abilities you kind of want those cards in the graveyard. Angler can be anything, even if its more anything its better than having to eat your skittles or whathaveyou in Black. This will see a good amount of play, and it will be really good. Often. I'm just not sure if I want this or a solid lump of size for very cheap you get from Angler. The other thing to absorb here is that if you cheat this guy into play he won't have the opportunity to get any abilities. I can see him showing up in graveyard oriented decks that are for some reason light on reanimation.

Archfiend of Depravity-
5 mana 5/4 flyers with upside are generally good. This one's upside is that he hampers strategies that want to grow wide. At any table of four players usually there's going to be someone doing a token/creature strategy that wants to have lots and lots of dudes. This guy is a respectable body for a reasonable cost whose enchantment hurts opponents only. He's perfect in Kaalia or other prison oriented decks.
 Also, the regular art is so much better than the alt art it hurts.

Palace Siege-
The Oversold Cemetery effect on this card is good, but wouldn't warrent a five mana price tag in EDH. The Polluted Bonds on the other hand is going to pay for itself in spades. Getting to cast Siphon Soul every upkeep is going to be pretty brutal. The obvious place for this card is in Oloro but it fits basically anywhere that you play Necropotence or other heavy life payment options. That it can switch between the two modes makes me want this in a B/W shell that eats lots of creatures, Teysa springs to mind.

Red:
Flamerush Rider-
Wow. Dash is a great mechanic that does a lot of very interesting things and has tons of room to grow. I am curious if they got into Fate Reforged and wanted to make more Raid cards and had just run out of ideas. Raid was a perfunctory mechanic but it had no tension to it. It essentially said, cast this card in your second main phase. There weren't any real trade offs aside from limited. Rush on the other hand is great. You can get the attack trigger NOW or have some pretty awesome effects later. It can trap you into needing to rush the creature over and over to keep getting the trigger. However, the ability in EDH to have global haste enablers makes cards with dash very dangerous since the all are going to have on attack triggers. Flamerush Rider is going to be played in lots of decks because the value is crazy high. One consequence of having multiple opponents is that usually someone is open to being attacked on the ground, and the trigger doesn't specify who the token is put into play attacking, letting you get tricky. Obviously having evasion for him would help but he should be able to do his thing most of the time. This guy is going to be really solid in Urabrask or Feldon. Paired with blue you can put him in decks that like Palinchron or other Dead-Eye Navigator targets. Dash also enables another axis of strategies, enters the battlefield effects. Something like Warstorm Surge is great with Dash in general, and with Flamerush in particular since he generates another trigger each turn he attacks. He is all the value.

Goblin Heelcutter-
This is going to be a type 2 card. The saving grace is goblin tribal decks, and even then its more for repeatable enters the battlefield effects.

Outpost Siege-
Now we're talking. This is totally worth four mana. This could have cost 3RR and still been played. Red doesn't have a density of card advantage cards, so everyone they print pushes us closer and closer being able to play mono-red value. Obviously the Dragon side is way more of a blow out than getting to play an extra card a turn. I just like that sometimes you have a top and no creatures and can just get to draw an extra card every turn. The Goblin Bombardment side is worded in such a way as to work with Dash and blinks, which is great. It also hits creatures, which is surprising. I shouldn't have to state how good this is in a deck like Marath but...this thing is really good in decks like Marath. This is a primer red card and fits all over the place.

Rageform-
This card is very very strange. It is ostensibly a four mana 2/2 double strike. The trick is that you can then turn the manifested card face up and straight up murder people if the creature was big enough. Its a risky card and probably won't see much if any play in EDH because of how many things have to go right for it. I award points for style though, and for templating this in such a way that I understood what it did in one reading.

Green:

Frontier Mastodon-
This is a 3 mana 3/2 that becomes a 3 mana 4/3 if you have ferocious. I like the idea that if you have ferocious and land this guy then you have two feroucious guys for other ferocious cards. That a lot of ferocious. Unfortunately, in EDH there are better deals.

Sandsteppe Mastodon-
Lots of Elephants in this set. This guy is a pretty good deal for seven mana. I just don't know where I would want this deal. Please comment if you can think of somewhere to put him.

Shamanistic Revelation-
Five mana sorceries that draw you cards don't usually inspire a lot of confidence since you'll need mana afterward to cast the cards unless you have a reliquary tower. Shamanistic Revelation I think has quite a few things that change that though. First, its green so having the mana afterward is certainly do-able between Cradle and bugs. The other effect has the potential to gain you enough life to survive to use the cards. The play pattern here seems to be that you spend your hand playing out mana bugs and whatever big dudes you have, then refill with this card and heal up from the first few turns of inaction. This feels like a green Sphinx's Revelation since you get cards and time to use them, and requires a lot of investment to make it worth it. This fits into any deck with the play pattern of Elves.

Temur War Shaman-
This is basically only good in decks heavy with morph/manifest. So basically nowhere in EDH. The only deck I can think of where I would play a decent amount of morph creatures and is green is Animar. And Animar doesn't need the effect. The alt art is probably better, but this is the only one that's close.

Whisperwood Elemental-
This is the manifest card I'm most interested in. Its ability to continually alter the top card of your deck works really well in conjuction with Sylvan Library in the absence of shuffles and provides a ton of wrath protection. That the face down creature aren't green is slightly annoying for effects like Regal Force, but getting through a large part of your deck is interesting in combination with graveyard recursion. Essentially manifest gets to draw you cards straight up in this situation. This probably goes in some G/B grindy attrition affair, something like Varolz or Jarad.

Multicolor:

Yasova Dragonclaw -
The first legend! I would hesitate to build this as deck in EDH, though Tiny Leaders is apparently a thing. The problem with it is the power restriction, and the timing restriction. And the mana cost. That's not to say that the card is bad. There are tons of utility creatures to take, use, and then feed to Gargadon. Its that it does cost you a significant amount. She does have trample and is very aggressive. If you're in the market for something attack oriented this is your gal. As a creature, Yasova requires 6 mana on your turn to take a creature with power 3 or less. Add in the color restriction and its going to take the alignment of the stars to have a place for Yasova.


Soulfire Grand Master-
This guy is really really cool. The design is something that we have been waiting to see for quite some time. The activated ability is expensive, so it can't be the point we rely on. So the question is, are there Jeskai decks that are viable that play large burn spells? I think the answer is a resounding yes. Unfortunately, you can't rescue spells that you fetch with Sunforger, but that's not to say the two are mutually exclusive. They both reward R/W/U spell heavy decks. I think this guy would get played more than it should be just because of how novel it is, but its restricted to Jeskai colors which pretty definitely line up with its abilities.

Ethereal Ambush-
As an instant and two cards this might be ok. Again, the viability of manifest is entirely reliant on how well it interacts with library manipulation, and how close it is to "draw a card". This one feels like it has a chance since its an instant and thus lets you cast it and then untap and unmorph immediately. I wouldn't put it in everything, but I'd like to try it in something like Momir Vig or something of that nature.

Kolaghan, the Storm's Fury-
I like this guy. As a general he's going to get Dashed out and put back into your hand frequently. That he triggers per dragon feels like a teaser for the next set, and it makes me feel like the unspoiled legendary dragons are also going to have an on-dragon trigger. He fits with tokens, haste, and aggression. Depending on how aggressive you want to be he can fit in Rakdos or Karrthus. On his own he works with B/Rs large number of cards designed to make the game end as fast as possible.

A good showing so far. This set looks like its trying to up the complexity level with some new, bizarre mechanics.