When would I play various cards from the Dominaria United spoiler?
We spent a lot of time meditating on this one last week; but didn't really answer this week's question very specifically.
The short answer is "almost any deck that can make Red mana".
I think the obvious place to start would be a mid-range or Rampy kind of Red creature deck, as Shivan Devastator can fill the mana hole at any point from turn two to turn fifty-two. But that is largely true for almost any deck that can cast it; not just a creature deck. This card is the height of flexibility, and in one of those turn fifty-two situations, represents a one-shot kill.
I like Shivan Devastator in the sideboard of a creatureless deck; because it keeps the opponent honest. No creature removal at all? My turn two 1/1 Devastator might just kill you. I think that'll by my favorite place (among so many) because Shivan Devastator will be best when it is not coming in against someone who just sided out a little removal.
Jaya, Fiery Negotiator
I really like this card!
Planeswalkers with four abilities tend to perform well in Standard, but I'm into it just for the first two.
[+1] How do you feel about Monastery Swiftspear? Jaya doesn't give you quite one, but ability one is close, and it builds loyalty to make them.
[-1] Jaya joins a number of Chandra variants, Outpost Siege, and kind of Experimental Frenzy as a four-mana permanent that just helps its controller draw extra cards. I love this ability! Despite being a "minus" ability, it allows you to play lands, which is a limitation that defined some of the four-mana permanents with a similar effect.
Both of Jaya's first two abilities are highly productive card advantage ones that you could want in obvious places. I feel like if you are going to play Jaya main deck, you will often [+1] for the Swiftspear proxy to defend her the turn she hits the battlefield. What comes after is up to you and the configuration of your deck; but she'll typically have 5+ Loyalty at that point, putting you in a great position to [-1] until she's down to one Loyalty.
Playing Jaya main deck is going to be about having the kind of deck that can take advantage of her built-in and implied synergies. You have a Planeswalker. It makes creatures. The creatures are friends with spells. If you can somehow get to [-8] you're really going to like having spells!
However, sideboard Jaya doesn't ask for very much. She will often be in your deck against an opponent who can't attack her [easily]. You might [-1] immediately to hit your next land drop, say if you tap for her on turn five. I think sideboard Jaya is going to be - is essentially intended to be - a [-1] machine, where the ability to dig a little bit is going to set you up for land drop after land drop. If you get a Monk or two, cool. But that's less of what she's about.
Maybe the question should be less "when" would I, but rather "what" would I pay for Temporal Firestorm... And I suppose I'd prefer about four mana. But that's not an option; so, five it is?
The idea of paying nine mana for this card seems kind of absurd to me; but I suppose we can game it out. If you're planning to phase out a Planeswalker, use it first! If you're phasing out a creture with a 187 effect, you're not going to get paid twice. Just saving your creature is going to have to be enough. This card is thoroughly not exciting to me on rate.
Is it possible Temporal Firestorm is the best option for sweeping in a Red control deck? It's possible, but kind of depressing if so. There are just giant threats that have more than 5 toughness that are not going to die.
What about Boros? I hope not.
Izzet? More likely than Boros; and less fatal than Mono-Red, if so. But in neither case am I excited to phase anything out... The kicker clauses have to be considered more as extra value than central to Temporal Fierestorm's value; which, again, seems unattractive.
This is a good card that will see play in a ton of different kinds of decks.
Good direct comparisons are Figure of Destiny and Ascendant Spirit; both of which were very happy to stick around at 4/4. Figure of Destiny was a standout in both White Weenie and a pre-Goblin Guide Mono-Red... Its 4/4 was pretty economical to get to.
Ascendant Spirit - played frequently today in Pioneer and a bit in Standard - is actually pretty happy to hang out at 2/3 ... 4/4 is like winning the lottery for that creature. As a Blue version, having mana open for permission or Spirits tricks is differently valuable than any of the other colors.
Evolved Sleeper can get to 3/3 Deathtouch for four mana over potentially three turns. That's a burly combat creature, especially depending on what kind of deck it's included in. Evolved Sleeper - and its ability to level up into Deathtouch at instant speed - can make blocking difficult, so it can be good in a creature deck/
But what seems more intruiging to me is this card in a Control deck. Just side one in and play it on turn one against an unsuspecting opponent who just took out a bunch of removal. Not only will your life go great, the Sleeper will eventually replace itself while becoming a meaningful threat on the battlefield.
This card will see play but probably won't be overly exciting in any of its homes. One option will be kind of a redundant two-mana Llanowar Elves (like how we see two copies of Sylvan Caryatid in Pioneer decks sometimes). It'll be a bit better in Ramp decks, where after it is no longer necessary for mana acceleration, Llanowar Loamspeaker can either set up a little more offense or start trading extra lands for opposing material. The fact that you can't block with a 3/3 severely limits how exciting this card will ever be.
For the most part these cards fail on rate. If I'm ever in a position where I'm considering if Jasmine Boreal of the Seven is the right card for my Selesnya deck, I'm severely reconsidering playing Selesnya.
Of these three cards, I think only Ramirez has any potential. One part is that he is Mulldrifter-ish on the way down. You get two Treasures immediately; so, from one angle he's a 4/3 for two mana. That's kind of insane (but still not a card you're going to play anywhere and everywhere). From another angle, you can tap out for him and still have mana "open" for counterplay. Again, kind of insane but not really against a beatdown deck or one with efficient on-table countersplay.
All that said, if your opponent isn't packing 3/x First Strikers and Searing Spears, Ramirez DePietro, Pillager isn't half bad. Against a or Control deck, resolving him is dandy in the abstract (four mana for 4 power; two Treasures every time)... And if you ever start hitting the opponent, they're probably going to lose. I suppose having a Pirate on the battlefield already and then tapping out for Ramirez would be cool! But I'd need to see more Pirates first.