So… as of now, pretty much all of the Ravnica Allegiance Spoilers are revealed. My impression is… a bit underwhelmed, unfortunately. The mana cost in general is too high and some of the mechanics are weak, if not downright awful.
Orzhov’s Afterlife mechanic is good in concept, but the cards are a bit weak. I would have recommend either making Afterlife mechanic trigger when the creature leave the battlefield rather than die, or simply generate more tokens (such as Seraph of the Scales, Knight of the Last Breath and Tithe Taker)
Simic’s Adapt is awful. I really don’t like the fact that you can only adapt once unless you have Biomancer’s Familiar or you transferred the counters to another creature first. The Adapt ability is also very expensive.
Azorius’ Addendum is also awful. The mechanic seems to be thrown in at the last minute just because every other guild have one. For instance, Emergency Powers only let you put one permanent for 7 mana, and that is a mythic’s addendum. At 7 mana, you should be able to put down 2-3 permanents. Meanwhile, Code of Constraint, which is an uncommon, cost 3 mana to give -4/-0, where as Downsize in Return to Ravnica and Stream of Unconsciousness in Morningtide cost on 1 with a chance to draw a card.
Gruul’s mechanic is okay. I would have preferred that most of the creatures with Riot mechanic have power exactly equal to the converted mana cost, so that the player have the choice of efficiency versus speed.
The only mechanic that wowed me is Rakdos Spectacle. In fact, a few of the cards I’m going to cover uses this mechanic.
For Blue, Sphinx of Foresight is a solid card at 4/4 for 4 and lets you Scry each turn. But the best thing about it is the ability to Scry 3 if this is in your opening hand. This is what blue is always good at: library manipulation.
Most of the mono-green card did not pique my interest. Incubation Druid lets you pump 3 mana, but only if you can put a +1/+1 counter on it, which requires workaround which slows down the ramp.
Red by far has the best cards.
Light Up the Stage significantly help Burn decks, which usually run out of cards by turn 3. The fact that you can use the exiled cards by the end of your next turn make this card awesome.
Finally, Spear Spewer is a really cheap pinger. The fact that this can trigger Spectacle makes this card really good in standard. I wonder what I can do with this in Modern…
For white, Angel of Grace is an interesting card. It has a strong body at 5/4 for 5 mana with Flying and Flash. But the best part is the Angel’s Grace ETB (enter-the-battlefield) effect. You can combine this with Eldrazi Displacer to get Angel’s Grace every turn, which sounds very interesting.
Biomancer’s Familiar is basically a creature version of Training Grounds that cost one more mana. The fact that it reduce the mana cost of activated abilities by 2 makes a lot of cards viable. In fact, you can check out the deck that I made with this card here.
As for Gruul Spellbreaker, 3/3 Trample for 3 mana with Riot is already strong. Giving itself and you hexproof during your turn is even better. While not overpowered, I can’t seem to hate this card.
Meanwhile, Warrant is quite a strong bounce card, considering that it bounce the creature to the library rather than the hand. This is quite good in tempo.
Prime Speaker Vannifar is basically a watered down version of Birthing Pod. While the ability no longer uses mana, replacing Phyrexian Green for a Blue mana significantly reduces the flexibility that Birthing Pod has as a mono-colored card.
Finally, Lavinia, Azorius Renegade is a decent card against Tron and Eldrazi as well as decks that uses mana dorks to accelerate. Someone also mentioned that it turns cards like Possibility Storm and Knowledge Pool into a control deck. Very interesting.
My final thoughts on Ravnica Allegiance is that it is an overall weak set with some interesting cards. I can see that most cards are good for Standard and EDH, but not much to be excited about for Modern.