Wow, after just a few more days we have even more stuff! This set's power level is pretty bonkers indeed. No sure things, but lots of "worth testings":
Deliver Unto Evil: In addition to having absolutely sick art and a sweet name, this card offers a very powerful effect that is a sort of hybrid of Yawgmoth's Will with the mindgames of Fact or Fiction and Gifts Ungiven (and with no restrictions so you can "cheese it" like folks do with Intuition). The cards I just mentioned are among MtG's most powerful and exciting in history, so I suspect this will make waves even ignoring the Bolas rider. And of course, with the Bolas rider this card is power nine levels of insanity...but that's so unlikely to work that it's more a sidegrade than a real thing.
The Elderspell: Despite the absolute hysteria happening over in the reveal thread, this is most likely just a sideboard card - but it is a hell of a sideboard card. Also interesting is some sort of Grixis Superfriends that uses this on their OWN walkers to instantly ultimate someone like Nicol Bolas, Dragon-God or Jace, the Mind Sculptor to win the game. That actually seems spicy enough to be worth testing in Modern, especially with a few other revealed cards today...
Ashiok, Dream Render: Speak of the devil, here's a walker I'd love to have kick around until I was ready to slam UBBBBBR for the instant God-Dragon Elderspell KO. A permanent Shadow of Doubt (or the most relevant part of Stranglehold) would have my attention at 1(U/B)(U/B) and might be worth sideboarding around given how devastating it is in a world of fetchlands. The fact that good ol' Ashi ALSO mills four cards and then exiles their entire graveyard up to five times before they bite the dust is just gravy and lets Ashiok do double-duty as both Grave hate and Tutor hate or help enable mill wins. I'd be tempted to say Ashiok was a sure thing if it wasn't for its wording preventing you from making mischief with Ghost Quarter and Field of Ruin and Path to Exile, but I still think its a contender.
Ugin, the Ineffable: Six mana is a lot, but making all colorless spells cost 2 less, blowing up permanents, and summoning 2/2 dorks that draw cards is a real card. I could see it being tested in Tron and Eldrazi decks just because of how powerful all his effects are.
God-Eternal Kefnet: Here me out! This card is VERY gross with extra turn effects. While it is itself a bit slow and easily disrupted and all the good top-of-library manipulation is largely banned, this can easily go off with an extra turn effect and goes infinite with an extra turn effect + Jace, the Mind Sculptor or Scroll Rack. Is it enough to take the "Taking Turns" deck out of meme status and into the realm of a real deck? I would love to test it.
Hawk7915, I think you're missing out on Bolas's Citadel in your Possible Players list. It not only creates entire combo decks around it that dodge graveyard hate, we've also tested it in Eggs and it looks like it can bring back that combo deck with the absurdly long turns.
Also, it's quite possible that the biggest way Neoform enables combos is in conjunction with Eldritch Evolution. We're building what's basically faster Grishoalbrand that dodges graveyard hate but is weaker to counterspells with both Neoform and Eldritch Evolution. The scary part is that Turn 2 wins are quite possible and Turn 1 wins are kinda Magical Christmas Land but will come up.
I should have mentioned Citadel although I'm not super sanguine (pun intended) on how good it's going to be.
1) A six mana sorcery speed combo enabler that is a Permanent (and thus vulnerable to disruption) has a HIGH bar to clear to be playable outside of Commander. That's not to say it's NEVER Happened (Amulet Bloom does have Hive Mind as its plan A kill condition), but even now today Mind Over Matter and Dream Halls aren't necessarily enabling Tier 1 archetypes and I'm unsure that Yawgmoth's Bargain would see significant play if unbanned. In a world of Through the Breached Eldrazi, Show and Tell-ed out Omniscience, Paradoxical Outcomes, and Ad Nauseaum this may just be too slow.
2) While this looks a bit like Bargain, it is mostly worse. It does enable you to go off right away which is nice, but in general artifacts are more vulnerable than enchantments, 3BBB is harder to cast than 4BB, and like Experimental Frenzy you end the chain of combo power if you hit too many lands.
If anywhere can make it work, it is eggs and it will especially "go off" if Lotus Petal can make its way to modern, but as it stands now I am not optimistic it'll get too much farther than "gimmick".
EDIT: Waidaminute...can you use this to cast Ancestral Vision, Living End, and (most importantly) Lotus Bloom without paying? Cause if so that is actually pretty bonkers.
This probably won't shake up Modern quite as much as Tarkir block, but it'll be a close second (especially looking at the block as a whole). It's one of the highest powered individual sets in recent memory, and might make the overall block one of the strongest ever.
Sure Things: I think these cards WILL see play in older formats.
Dovin's Veto: Negate is mostly a sideboard card (it sees occasional maindeck play in Modern), but for Azorius decks this is a pure upgrade especially control decks where it can be a "hard no" to powerful planeswalkers and combo pieces.
Liliana's Triumph: Diabolic Edict in Modern is a reasonably big deal in a format with powerful hexproof threats so this will be a sideboard card at worst. The upside you get from running it alongside a Liliana (and there are numerous highly playable Lilis in all formats) is a real benefit for "Rock" and "Grixis Shadow"-style decks.
Karn, the Great Creator: A one-sided Null Rod would be worth sideboard consideration in older formats. Add on the ability to enable various combos and kills with his +1 and you get a spicy meatball. Add on the ability to pull a Mastermind's Acquisition and pull wincons out of the sideboard (including Mycosynth Lattice for a total lockdown) and you have a card with some real mainboard potential for all the big colorless decks in older formats.
Tomik, Distinguished Advokist: Hard shutdown of Depths decks (can't target depths with Thespian's Stage and most Dredge decks. A 2/3 flying body is also a lot better than the average hatebear and wears equipment well. His type is super relevant for older formats as well. Will be popular in most W/x decks.
Possible Players: I think these cards will be worth testing, but aren't sure things.
Teferi, Time Raveler and Vivien, Champion of the Wilds: These two are similar in that they offer extremely powerful abilities that manipulate your ability to play cards outside your turn, they are three CMC, and they can replace themselves. However, they don't seem to slot into any particular deck at the moment. I think they're both worth testing for sure.
Nissa's Triumph: This card is wildly unplayable without Nissa on the battlefield, but a triple Sylvan Scrying (which, conveniently, finds all three Tron pieces) is a big deal. I will be curious if the upside on this card is high enough to merit testing adding some Nissas to Scapeshift, Tron, and Depths decks to enable it.
Ral, Storm Conduit: This creates some infinite comboes that win on the spot, and those combos are easier to trigger in older formats (for example, it is instantly infinite with Fork. I think it'll be a big player in Standard, but we'll see if it is fast enough for Modern and Legacy.
Saheeli, Sublime Artificer: Is a more splashable, more resilient Young Pyromancer that can also do various combo shenanigans worth an extra mana? I don't know, but I think it is worth testing.
Angrath's Rampage: If this was an instant it'd be a sure thing. As a sorcery, I am not sure it is worth playing over Liliana's Triumph, Terminate, or Abrade.
Dovin, Hand of Control: Another powerful effect that is a bit more than its competitors but comes with some upside. More likely to see a ton of play in Commander than Modern but worth listing.
Finale of Promise: Hey, look, another card that enables comboes with Ancestral Vision and Living End! This is also a heck of a payoff for a big mana deck. I'm a little cooler on it because Electrodominance ended up fizzling, but this generally has a higher ceiling that Dominance even if it is slower and has a lower floor.
Dreadhorde Arcanist: Doesn't necessarily slot into a deck neatly (seems good but not great in Burn and burn is tight on slots), but could team up with Monastery Swiftspear and other Heroic/Prowess cards to make a whole new archetype in older formats.
Dreadhorde Invasion: Bitterblossom hasn't been the rockstar we expected with an unban, and this is mostly worse...except that Zombie is waaaaay more relevant than Fairy as a typing. Worth a look for sure.
Vivien's Arkbow: I think this is bad, but it is also interesting and worth testing.
Neoform: How much better and more able to enable comboes is Neoform compared to Eldritch Evolution? Unclear, but I'm sure lots of folks will test it.
Deliver Unto Evil: In addition to having absolutely sick art and a sweet name, this card offers a very powerful effect that is a sort of hybrid of Yawgmoth's Will with the mindgames of Fact or Fiction and Gifts Ungiven (and with no restrictions so you can "cheese it" like folks do with Intuition). The cards I just mentioned are among MtG's most powerful and exciting in history, so I suspect this will make waves even ignoring the Bolas rider. And of course, with the Bolas rider this card is power nine levels of insanity...but that's so unlikely to work that it's more a sidegrade than a real thing.
The Elderspell: Despite the absolute hysteria happening over in the reveal thread, this is most likely just a sideboard card - but it is a hell of a sideboard card. Also interesting is some sort of Grixis Superfriends that uses this on their OWN walkers to instantly ultimate someone like Nicol Bolas, Dragon-God or Jace, the Mind Sculptor to win the game. That actually seems spicy enough to be worth testing in Modern, especially with a few other revealed cards today...
Ashiok, Dream Render: Speak of the devil, here's a walker I'd love to have kick around until I was ready to slam UBBBBBR for the instant God-Dragon Elderspell KO. A permanent Shadow of Doubt (or the most relevant part of Stranglehold) would have my attention at 1(U/B)(U/B) and might be worth sideboarding around given how devastating it is in a world of fetchlands. The fact that good ol' Ashi ALSO mills four cards and then exiles their entire graveyard up to five times before they bite the dust is just gravy and lets Ashiok do double-duty as both Grave hate and Tutor hate or help enable mill wins. I'd be tempted to say Ashiok was a sure thing if it wasn't for its wording preventing you from making mischief with Ghost Quarter and Field of Ruin and Path to Exile, but I still think its a contender.
Ugin, the Ineffable: Six mana is a lot, but making all colorless spells cost 2 less, blowing up permanents, and summoning 2/2 dorks that draw cards is a real card. I could see it being tested in Tron and Eldrazi decks just because of how powerful all his effects are.
God-Eternal Kefnet: Here me out! This card is VERY gross with extra turn effects. While it is itself a bit slow and easily disrupted and all the good top-of-library manipulation is largely banned, this can easily go off with an extra turn effect and goes infinite with an extra turn effect + Jace, the Mind Sculptor or Scroll Rack. Is it enough to take the "Taking Turns" deck out of meme status and into the realm of a real deck? I would love to test it.
RCRDaretti: Superfriends Forever RCR
WGBDoran: Ent-mootWBG
GGGMultani: Group Bear HugGGG
GB(B/G)The Gitrog Monster: Dredgefall DurdleGB(B/G)
RGWGahiji, the Honored Group Hug MonsterRGW
UB(U/B)Yuriko, Ninja Trinket AggroUB(U/B)
WUBRGAtogatog: Assembling a OHKOWUBRG
I should have mentioned Citadel although I'm not super sanguine (pun intended) on how good it's going to be.
1) A six mana sorcery speed combo enabler that is a Permanent (and thus vulnerable to disruption) has a HIGH bar to clear to be playable outside of Commander. That's not to say it's NEVER Happened (Amulet Bloom does have Hive Mind as its plan A kill condition), but even now today Mind Over Matter and Dream Halls aren't necessarily enabling Tier 1 archetypes and I'm unsure that Yawgmoth's Bargain would see significant play if unbanned. In a world of Through the Breached Eldrazi, Show and Tell-ed out Omniscience, Paradoxical Outcomes, and Ad Nauseaum this may just be too slow.
2) While this looks a bit like Bargain, it is mostly worse. It does enable you to go off right away which is nice, but in general artifacts are more vulnerable than enchantments, 3BBB is harder to cast than 4BB, and like Experimental Frenzy you end the chain of combo power if you hit too many lands.
If anywhere can make it work, it is eggs and it will especially "go off" if Lotus Petal can make its way to modern, but as it stands now I am not optimistic it'll get too much farther than "gimmick".
EDIT: Waidaminute...can you use this to cast Ancestral Vision, Living End, and (most importantly) Lotus Bloom without paying? Cause if so that is actually pretty bonkers.
RCRDaretti: Superfriends Forever RCR
WGBDoran: Ent-mootWBG
GGGMultani: Group Bear HugGGG
GB(B/G)The Gitrog Monster: Dredgefall DurdleGB(B/G)
RGWGahiji, the Honored Group Hug MonsterRGW
UB(U/B)Yuriko, Ninja Trinket AggroUB(U/B)
WUBRGAtogatog: Assembling a OHKOWUBRG
Sure Things: I think these cards WILL see play in older formats.
Dovin's Veto: Negate is mostly a sideboard card (it sees occasional maindeck play in Modern), but for Azorius decks this is a pure upgrade especially control decks where it can be a "hard no" to powerful planeswalkers and combo pieces.
Liliana's Triumph: Diabolic Edict in Modern is a reasonably big deal in a format with powerful hexproof threats so this will be a sideboard card at worst. The upside you get from running it alongside a Liliana (and there are numerous highly playable Lilis in all formats) is a real benefit for "Rock" and "Grixis Shadow"-style decks.
Karn, the Great Creator: A one-sided Null Rod would be worth sideboard consideration in older formats. Add on the ability to enable various combos and kills with his +1 and you get a spicy meatball. Add on the ability to pull a Mastermind's Acquisition and pull wincons out of the sideboard (including Mycosynth Lattice for a total lockdown) and you have a card with some real mainboard potential for all the big colorless decks in older formats.
Tomik, Distinguished Advokist: Hard shutdown of Depths decks (can't target depths with Thespian's Stage and most Dredge decks. A 2/3 flying body is also a lot better than the average hatebear and wears equipment well. His type is super relevant for older formats as well. Will be popular in most W/x decks.
Possible Players: I think these cards will be worth testing, but aren't sure things.
Teferi, Time Raveler and Vivien, Champion of the Wilds: These two are similar in that they offer extremely powerful abilities that manipulate your ability to play cards outside your turn, they are three CMC, and they can replace themselves. However, they don't seem to slot into any particular deck at the moment. I think they're both worth testing for sure.
Nissa's Triumph: This card is wildly unplayable without Nissa on the battlefield, but a triple Sylvan Scrying (which, conveniently, finds all three Tron pieces) is a big deal. I will be curious if the upside on this card is high enough to merit testing adding some Nissas to Scapeshift, Tron, and Depths decks to enable it.
Ral, Storm Conduit: This creates some infinite comboes that win on the spot, and those combos are easier to trigger in older formats (for example, it is instantly infinite with Fork. I think it'll be a big player in Standard, but we'll see if it is fast enough for Modern and Legacy.
Saheeli, Sublime Artificer: Is a more splashable, more resilient Young Pyromancer that can also do various combo shenanigans worth an extra mana? I don't know, but I think it is worth testing.
Angrath's Rampage: If this was an instant it'd be a sure thing. As a sorcery, I am not sure it is worth playing over Liliana's Triumph, Terminate, or Abrade.
Dovin, Hand of Control: Another powerful effect that is a bit more than its competitors but comes with some upside. More likely to see a ton of play in Commander than Modern but worth listing.
Finale of Promise: Hey, look, another card that enables comboes with Ancestral Vision and Living End! This is also a heck of a payoff for a big mana deck. I'm a little cooler on it because Electrodominance ended up fizzling, but this generally has a higher ceiling that Dominance even if it is slower and has a lower floor.
Dreadhorde Arcanist: Doesn't necessarily slot into a deck neatly (seems good but not great in Burn and burn is tight on slots), but could team up with Monastery Swiftspear and other Heroic/Prowess cards to make a whole new archetype in older formats.
Dreadhorde Invasion: Bitterblossom hasn't been the rockstar we expected with an unban, and this is mostly worse...except that Zombie is waaaaay more relevant than Fairy as a typing. Worth a look for sure.
Vivien's Arkbow: I think this is bad, but it is also interesting and worth testing.
Neoform: How much better and more able to enable comboes is Neoform compared to Eldritch Evolution? Unclear, but I'm sure lots of folks will test it.
RCRDaretti: Superfriends Forever RCR
WGBDoran: Ent-mootWBG
GGGMultani: Group Bear HugGGG
GB(B/G)The Gitrog Monster: Dredgefall DurdleGB(B/G)
RGWGahiji, the Honored Group Hug MonsterRGW
UB(U/B)Yuriko, Ninja Trinket AggroUB(U/B)
WUBRGAtogatog: Assembling a OHKOWUBRG