This card is Polymorph without the sacrifice (Wild) and/or one-sided Show and Tell (Free). The only thing keeping this from seeing play in Legacy would be its cost. I don't play Legacy, so I don't know of any decks that would support it.
I think that going base Bant, the tools are there to go full 5 color between the color fixing of Oath of Nissa, the mana cheating of Deploy the Gatewatch, and Blue's draw/filtering. Chandra and Sorin are the strongest individual walkers, so it would be a shame to leave them out of a deck like this.
Turn 1. 1 Green Source + BoP/Hierarch
Turn 2. Land + Allosaurus Rider + 2 Green Cards + EE
That is 7 cards, but that is doable. Reanimator decks in Legacy need more for the same result, a game-winning creature (Griselbrand, Iona, Elesh Norn, etc) on board. This isn't MagicChristmasLand. It is genuinely scary.
This is one of three lands that I know of that can ramp without a spell. The other two cost 5 to ramp, while this costs 3. The other two saw play, so will this.
If I were to list all the cards I like from this set so far, it would probably be longer than the list of cards I don't like. If we are talking absolute favorites so far, my top three would be:
It seems best compared to Journey to Nowhere, a two-mana, remove any creature at sorcery speed spell with a downside. Journey can be removed, giving them the creature back, where this leaves behind a token that can be cashed in at a later point for a card. Journey doesn't see much play in Modern, so I doubt this will either despite a smaller downside, but it seems solid enough for Standard.
I meant to post this last week, but got caught up doing other things. There have been a few cards that hint at reprints that, at least in my opinion, should happen in SoI. The phrase "urge to feed" is used on Heir of Falkenrath and Urge to Feed just happens to be a very potent Vampire tribal card. The other obvious one to me is Avacynian Missionaries turning into Lunarch Inquisitors when equipped. That screams Inquisitor's Flail. Did anybody else pick up on flavor that might hint at possible reprints?
This card makes me sad. It is just so close to being playable, but yet so far away. Having three costs seems to be a deal-breaker in terms of playability. Being a Soul Sister at triple the price is not exciting either. I will definitely try it in my Displacer Combo deck, but I don't have high hopes for it.
In terms of combo, there really is only one: Eldrazi Displacer+Brood Monitor. There are however a ton of ways to build around the combo. First you pick a card or cards that can kill with either ETB, LTB or Death triggers.
Kill Cards
Some of those are terrible options, but all of them can give you a win when paired with the combo.
After that you have to decide what kind of deck you want to build around that win condition. Abzan Aristocrats already runs Zulaport Cutthroat, and sometimes Rot Shambler, so slotting the combo into that deck is most obvious. You could go Astral Slide style with Morph/Manifest. You could build a control deck that stalls and digs for combo pieces. You could build a value deck that abuses ETBs and has the combo as an "Oops, I win". This card is glorious in that it does amazing things without building the deck by itself.
Turn 2. Land + Allosaurus Rider + 2 Green Cards + EE
That is 7 cards, but that is doable. Reanimator decks in Legacy need more for the same result, a game-winning creature (Griselbrand, Iona, Elesh Norn, etc) on board. This isn't MagicChristmasLand. It is genuinely scary.
Kill Cards
Some of those are terrible options, but all of them can give you a win when paired with the combo.
After that you have to decide what kind of deck you want to build around that win condition. Abzan Aristocrats already runs Zulaport Cutthroat, and sometimes Rot Shambler, so slotting the combo into that deck is most obvious. You could go Astral Slide style with Morph/Manifest. You could build a control deck that stalls and digs for combo pieces. You could build a value deck that abuses ETBs and has the combo as an "Oops, I win". This card is glorious in that it does amazing things without building the deck by itself.
Eldrazi Displacer + Brood Monitor + Zulaport Cutthroat
The fact that Displacer is strong enough to run on its own makes it especially scary.